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Neuroendocrine carcinomas (NEC) of the breast are exceedingly rare tumors, which are classified in the WHO system as small cell (SCNEC) and large cell (LCNEC) carcinoma based on indistinguishable features from their lung counterparts. In contrast to lung and enteropancreatic NEC, the genomics of breast NEC have not been well-characterized. In this study, we examined the clinicopathologic, immunohistochemical, and genetic features of 13 breast NEC (7 SCNEC, 4 LCNEC, 2 NEC with ambiguous small versus large cell morphology [ANEC]). Co-alterations of TP53 and RB1 were identified in 86% (6/7) SCNEC, 100% (2/2) ANEC, and 50% (2/4) LCNEC. The one SCNEC without TP53/RB1 alteration had other p53 pathway aberrations (MDM2 and MDM4 amplification) and was immunohistochemically RB negative. PIK3CA/PTEN pathway alterations and ZNF703 amplifications were each identified in 46% (6/13) NEC. Two tumors (1 SCNEC, 1 LCNEC) were CDH1 mutated. By immunohistochemistry, 100% SCNEC (6/6) and ANEC (2/2) and 50% (2/4) LCNEC (83% NEC) showed RB loss, compared to 0% (0/8) grade 3 neuroendocrine tumors (NET) (p

We evaluated the association of percent mammographic density (PMD), absolute dense area (DA), and non-dense area (NDA) with risk of “intrinsic” molecular breast cancer (BC) subtypes. We pooled 3492 invasive BC and 10,148 controls across six studies with density measures from prediagnostic, digitized film-screen mammograms. We classified BC tumors into subtypes [63% Luminal A, 21% Luminal B, 5% HER2 expressing, and 11% as triple negative (TN)] using information on estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), and tumor grade. We used polytomous logistic regression to calculate odds ratio (OR) and 95% confidence intervals (CI) for density measures (per SD) across the subtypes compared to controls, adjusting for age, body mass index and study, and examined differences by age group. All density measures were similarly associated with BC risk across subtypes. Significant interaction of PMD by age (P = 0.001) was observed for Luminal A tumors, with stronger effect sizes seen for younger women

Stromal stiffening accompanies malignancy, compromises treatment and promotes tumour aggression. Clarifying the molecular nature and the factors that regulate stromal stiffening in tumours should identify biomarkers to stratify patients for therapy and interventions to improve outcome. We profiled lysyl hydroxylase-mediated and lysyl oxidase-mediated collagen crosslinks and quantified the greatest abundance of total and complex collagen crosslinks in aggressive human breast cancer subtypes with the stiffest stroma. These tissues harbour the highest number of tumour-associated macrophages, whose therapeutic ablation in experimental models reduced metastasis, and decreased collagen crosslinks and stromal stiffening. Epithelial-targeted expression of the crosslinking enzyme, lysyl oxidase, had no impact on collagen crosslinking in PyMT mammary tumours, whereas stromal cell targeting did. Stromal cells in microdissected human tumours expressed the highest level of collagen crosslinking enzymes. Immunohistochemical analysis of biopsies from a cohort of patients with breast cancer revealed that stromal expression of lysyl hydroxylase 2, an enzyme that induces hydroxylysine aldehyde-derived collagen crosslinks and stromal stiffening, correlated significantly with disease specific mortality. The findings link tissue inflammation, stromal cell-mediated collagen crosslinking and stiffening to tumour aggression and identify lysyl hydroxylase 2 as a stromal biomarker.

Background: Previous studies have independently validated the prognostic relevance of residual cancer burden (RCB) after neoadjuvant chemotherapy. We used results from several independent cohorts in a pooled patient-level analysis to evaluate the relationship of RCB with long-term prognosis across different phenotypic subtypes of breast cancer, to assess generalisability in a broad range of practice settings. Methods: In this pooled analysis, 12 institutes and trials in Europe and the USA were identified by personal communications with site investigators. We obtained participant-level RCB results, and data on clinical and pathological stage, tumour subtype and grade, and treatment and follow-up in November, 2019, from patients (aged ≥18 years) with primary stage I–III breast cancer treated with neoadjuvant chemotherapy followed by surgery. We assessed the association between the continuous RCB score and the primary study outcome, event-free survival, using mixed-effects Cox models with the incorporation of random RCB and cohort effects to account for between-study heterogeneity, and stratification to account for differences in baseline hazard across cancer subtypes defined by hormone receptor status and HER2 status. The association was further evaluated within each breast cancer subtype in multivariable analyses incorporating random RCB and cohort effects and adjustments for age and pretreatment clinical T category, nodal status, and tumour grade. Kaplan-Meier estimates of event-free survival at 3, 5, and 10 years were computed for each RCB class within each subtype. Findings: We analysed participant-level data from 5161 patients treated with neoadjuvant chemotherapy between Sept 12, 1994, and Feb 11, 2019. Median age was 49 years (IQR 20–80). 1164 event-free survival events occurred during follow-up (median follow-up 56 months [IQR 0–186]). RCB score was prognostic within each breast cancer subtype, with higher RCB score significantly associated with worse event-free survival. The univariable hazard ratio (HR) associated with one unit increase in RCB ranged from 1·55 (95% CI 1·41–1·71) for hormone receptor-positive, HER2-negative patients to 2·16 (1·79–2·61) for the hormone receptor-negative, HER2-positive group (with or without HER2-targeted therapy; p

Tall cell carcinoma with reverse polarity is a rare subtype of breast carcinoma with solid and papillary growth and nuclear features reminiscent of those of the tall cell variant of papillary thyroid carcinoma. These tumors harbor recurrent IDH2 R172 hotspot mutations or TET2 mutations, co-occurring with mutations in PI3K pathway genes. Diagnosis of tall cell carcinomas with reverse polarity is challenging in view of their rarity and the range of differential diagnosis. We sought to determine the sensitivity and specificity of IDH2 R172 immunohistochemistry for the detection of IDH2 R172 hotspot mutations in this entity. We evaluated 14 tall cell carcinomas with reverse polarity (ten excision and five core needle biopsy specimens), 13 intraductal papillomas, 16 solid papillary carcinomas, and 5 encapsulated papillary carcinomas by Sanger sequencing of the IDH2 R172 hotspot locus and of exons 9 and 20 of PIK3CA, and by immunohistochemistry using monoclonal antibodies (11C8B1) to the IDH2 R172S mutation. The 14 tall cell carcinomas with reverse polarity studied harbored IDH2 R172 hotspot mutations, which co-occurred with PIK3CA hotspot mutations in 50% of cases. None of the other papillary neoplasms analyzed displayed IDH2 R172 mutations, however PIK3CA hotspot mutations were detected in 54% of intraductal papillomas, 6% of solid papillary carcinomas, and 20% of encapsulated papillary carcinomas tested. Immunohistochemical analysis with anti-IDH2 R172S antibodies (11C8B1) detected IDH2 R172 mutated protein in 93% (14/15) of tall cell carcinomas with reverse polarity samples including excision (n = 9/10) and core needle biopsy specimens (n = 5), whereas the remaining papillary neoplasms (n = 34) were negative. Our findings demonstrate that immunohistochemical analysis of IDH2 R172 is highly sensitive and specific for the detection of IDH2 R172 hotspot mutations, and likely suitable as a diagnostic tool in the evaluation of excision and core needle biopsy material of tall cell carcinomas with reverse polarity.

Pleomorphic invasive lobular carcinoma (ILC) has long been thought to have worse outcomes than classic ILC and is therefore often treated with chemotherapy. However, recent data question the utility of the pleomorphic designation, as the poor outcomes seen may be related to other associated high-risk features. Importantly, mitotic count may better define a subset of ILC with high risk of recurrence. We sought to determine the impact of pleomorphic histology versus mitotic count on disease-free survival (DFS) in pure ILC. Additionally, we evaluated whether pleomorphic histology was associated with receipt of chemotherapy when adjusting for other factors. We analyzed a cohort of 475 patients with stage I–III pure ILC. We used Kaplan–Meier estimates, and Cox proportional hazards and logistic regression for multivariate analyses. Pleomorphic histology was confirmed by central pathology review. In a multivariate model, pleomorphic histology was not associated with reduced DFS. Only mitotic score, receptor subtype, and pathologic stage were independently and significantly associated with DFS. Patients with pleomorphic ILC were significantly more likely to receive chemotherapy than patients with classic ILC (adjusted odds ratio 2.96, p = 0.026). The pleomorphic designation in ILC does not have clinical utility and should not be used to determine therapy. Rather, mitotic count identified clear prognostic groups in this cohort of pure ILC.

ImportancePathologic complete response (pCR) after neoadjuvant chemotherapy (NAC) in breast cancer strongly correlates with overall survival and has become the standard end point in neoadjuvant trials. However, there is controversy regarding whether the definition of pCR should exclude or permit the presence of residual ductal carcinoma in situ (DCIS).ObjectiveTo examine the association of residual DCIS in surgical specimens after neoadjuvant chemotherapy for breast cancer with survival end points to inform standards for the assessment of pathologic complete response.Design, Setting, and ParticipantsThe study team analyzed the association of residual DCIS after NAC with 3-year event-free survival (EFS), distant recurrence-free survival (DRFS), and local-regional recurrence (LRR) in the I-SPY2 trial, an adaptive neoadjuvant platform trial for patients with breast cancer at high risk of recurrence. This is a retrospective analysis of clinical specimens and data from the ongoing I-SPY2 adaptive platform trial of novel therapeutics on a background of standard of care for early breast cancer. I-SPY2 participants are adult women diagnosed with stage II/III breast cancer at high risk of recurrence.InterventionsParticipants were randomized to receive taxane and anthracycline-based neoadjuvant therapy with or without 1 of 10 investigational agents, followed by definitive surgery.Main Outcomes and MeasuresThe presence of DCIS and EFS, DRFS, and LRR.ResultsThe study team identified 933 I-SPY2 participants (aged 24 to 77 years) with complete pathology and follow-up data. Median follow-up time was 3.9 years; 337 participants (36%) had no residual invasive disease (residual cancer burden 0, or pCR). Of the 337 participants with pCR, 70 (21%) had residual DCIS, which varied significantly by tumor-receptor subtype; residual DCIS was present in 8.5% of triple negative tumors, 15.6% of hormone-receptor positive tumors, and 36.6% of ERBB2-positive tumors. Among those participants with pCR, there was no significant difference in EFS, DRFS, or LRR based on presence or absence of residual DCIS.Conclusions and RelevanceThe analysis supports the definition of pCR as the absence of invasive disease after NAC regardless of the presence or absence of DCIS.Trial RegistrationClinicalTrials.gov Identifier NCT01042379.

Importance Residual cancer burden (RCB) distributions may improve the interpretation of efficacy in neoadjuvant breast cancer trials. Objective To compare RCB distributions between randomized control and investigational treatments within subtypes of breast cancer and explore the relationship with survival. Design, Setting, and Participants The I-SPY2 is a multicenter, platform adaptive, randomized clinical trial in the US that compares, by subtype, investigational agents in combination with chemotherapy vs chemotherapy alone in adult women with stage 2/3 breast cancer at high risk of early recurrence. Investigational treatments graduated in a prespecified subtype if there was 85% or greater predicted probability of higher rate of pathologic complete response (pCR) in a confirmatory, 300-patient, 1:1 randomized, neoadjuvant trial in that subtype. Evaluation of a secondary end point was reported from the 10 investigational agents tested in the I-SPY2 trial from March 200 through 2016, and analyzed as of September 9, 2020. The analysis plan included modeling of RCB within subtypes defined by hormone receptor (HR) andERBB2 status and compared control treatments with investigational treatments that graduated and those that did not graduate. Interventions Neoadjuvant paclitaxel plus/minus 1 of several investigational agents for 12 weeks, then 12 weeks of cyclophosphamide/doxorubicin chemotherapy followed by surgery. Main Outcomes and Measures Residual cancer burden (pathological measure of residual disease) and event-free survival (EFS). Results A total of 938 women (mean [SD] age, 49 [11] years; 66 [7%] Asian, 103 [11%] Black, and 750 [80%] White individuals) from the first 10 investigational agents were included, with a median follow-up of 52 months (IQR, 29 months). Event-free survival worsened significantly per unit of RCB in every subtype of breast cancer (HR-positive/ERBB2-negative: hazard ratio [HZR], 1.75; 95% CI, 1.45-2.16; HR-positive/ERBB2-positive: HZR, 1.55; 95% CI, 1.18-2.05; HR-negative/ERBB2-positive: HZR, 2.39; 95% CI, 1.64-3.49; HR-negative/ERBB2-negative: HZR, 1.99; 95% CI, 1.71-2.31). Prognostic information from RCB was similar from treatments that graduated (HZR, 2.00; 95% CI, 1.57-2.55; 254 [27%]), did not graduate (HZR, 1.87; 95% CI, 1.61-2.17; 486 [52%]), or were control (HZR, 1.79; 95% CI, 1.42-2.26; 198 [21%]). Investigational treatments significantly lowered RCB in HR-negative/ERBB2-negative (graduated and nongraduated treatments) andERBB2-positive subtypes (graduated treatments), with improved EFS (HZR, 0.61; 95% CI, 0.41-0.93) in the exploratory analysis. Conclusions and Relevance In this randomized clinical trial, the prognostic significance of RCB was consistent regardless of subtype and treatment. Effective neoadjuvant treatments shifted the distribution of RCB in addition to increasing pCR rate and appeared to improve EFS. Using a standardized quantitative method to measure response advances the interpretation of efficacy. Trial Registration ClinicalTrials.gov Identifier:NCT01042379

Secretory carcinoma is a special-type breast carcinoma underpinned by a recurrent t(12;15)(p13;q25) translocation resulting in ETV6-NTRK3 gene fusion. Immunohistochemistry (IHC) using a pan-TRK antibody has been recently shown to help identify NTRK rearrangements in other tumor types. The purpose of this study was to assess the diagnostic utility of pan-TRK IHC in secretory carcinoma of the breast. Pan-TRK IHC was performed using a rabbit monoclonal antibody on whole sections of 24 breast secretory carcinomas and tissue microarray sections of other breast carcinoma types (n=203) and histologic mimics (n=15). Cases were assessed for staining intensity and localization. The 24 patients with secretory carcinoma had a median age of 44 years and a median tumor size of 1.0 cm. ETV6 fluorescence in situ hybridization was positive in all cases tested (n=20). Twenty-three cases (95.8%) showed staining with pan-TRK, which was exclusively nuclear in 19, primarily nuclear with weak cytoplasmic staining in 3, and primarily cytoplasmic with focal nuclear staining in 1. The nuclear staining was diffuse in 17 and at least focally strong in 17. The only pan-TRK negative case was a core biopsy with limited tumor. Among the 203 nonsecretory carcinomas, 21 (10.3%) showed focal, weak nuclear staining in

The natural history and optimal treatment of pleomorphic (PLCIS) and florid (FLCIS) lobular carcinoma in situ variants remains uncertain. We reviewed the clinicopathologic features and management of LCIS variants at our institution over a 20-year period. Of 85 cases (61 PLCIS, 24 FLCIS), 77% were associated with invasive carcinoma (84% lobular, 13% ductal/lobular, 3% ductal) and only 17% (9 PLCIS, 5 FLCIS) were pure. Most (81%) invasive carcinomas were grade 2, with all grade 3/pleomorphic invasive lobular carcinomas (ILC) associated with PLCIS, and all grade 1 tumors associated with FLCIS. PLCIS-associated invasive carcinomas were more often ER- (21%) or HER2+ (14%) than FLCIS-associated tumors (100% ER+, 6% HER2+). LCIS variants were unifocal and co-localized with invasive carcinoma in 20/20 selected spatially mapped cases, whereas classic LCIS (CLCIS) was multifocal with wider distribution (10/17). Of 21 pure LCIS variants on core biopsy, all represented the radiographic (95%) or palpable (5%) target. The excisional upgrade rate was similar for PLCIS (38%) and FLCIS (33%). Pure LCIS variants on core biopsy were often (20%) HER2+ and had a higher Ki-67-index than synchronous CLCIS (P=0.002). Lower ER expression in LCIS variants versus CLCIS was due to ER- apocrine PLCIS. ER and HER2 were consistently concordant between LCIS variants and upgraded ILC but discordant between synchronous CLCIS and LCIS variants in 5/14 (36%). Pure LCIS variants were excised to negative margins and frequently (58%) treated with endocrine but not radiation therapy without recurrences. In summary, PLCIS and FLCIS demonstrate features of direct precursor lesions warranting surgical excision.

Aims Mucoepidermoid carcinomas (MEC) are the most common malignant neoplasms of salivary glands, but are uncommon in other sites. Salivary gland MEC are most frequently associated with CRTC1-MAML2 translocations. Exceedingly rare MEC of the breast demonstrate a basal-like and often triple (oestrogen and progesterone receptor, HER2)-negative immunophenotype, with a single case previously reported to show MAML2 rearrangement, although the fusion partner was not known. Comprehensive genomic studies of breast MEC are lacking. In this study, we analysed the immunophenotype and molecular landscape of two breast MEC to elucidate the pathogenesis of these rare tumours. Methods and results Two breast MEC were subjected to capture-based next-generation DNA sequencing of 479 cancer-related genes. The presence of the CRTC1-MAML2 fusion transcript was interrogated by reverse transcriptase-polymerase chain reaction. In addition, the immunoprofiles of breast MEC were compared to salivary gland MEC. Both breast MEC harboured CRTC1-MAML2 fusions. In contrast to most triple-negative breast carcinomas of no special type, the mutational burden of MEC was very low, with one case demonstrating only an inactivating SETD2 mutation, and the other harbouring no somatic variants in genes on the panel. No copy number alterations were identified. The immunoprofiles of breast and salivary gland MEC were overlapping, but not identical. Conclusions The findings highlight MEC as a breast cancer subtype more closely related to its salivary gland counterpart than to basal-like/triple-negative breast cancers of no special type.

Women with dense breasts have an increased lifetime risk of malignancy that has been attributed to a higher epithelial density. Quantitative proteomics, collagen analysis, and mechanical measurements in normal tissue revealed that stroma in the high-density breast contains more oriented, fibrillar collagen that is stiffer and correlates with higher epithelial cell density. microRNA (miR) profiling of breast tissue identified miR-203 as a matrix stiffness-repressed transcript that is downregulated by collagen density and reduced in the breast epithelium of women with high mammographic density. Culture studies demonstrated that ZNF217 mediates a matrix stiffness- and collagen density-induced increase in Akt activity and mammary epithelial cell proliferation. Manipulation of the epithelium in a mouse model of mammographic density supported a causal relationship between stromal stiffness, reduced miR-203, higher levels of the murine homolog Zfp217, and increased Akt activity and mammary epithelial proliferation. ZNF217 was also increased in the normal breast epithelium of women with high mammographic density, correlated positively with epithelial proliferation and density, and inversely with miR-203. The findings identify ZNF217 as a potential target toward which preexisting therapies, such as the Akt inhibitor triciribine, could be used as a chemopreventive agent to reduce cancer risk in women with high mammographic density.

PURPOSE Primary endocrine therapy for ductal carcinoma in situ (DCIS) as a potential alternative to surgery has been understudied. This trial explored the feasibility of a short-term course of letrozole and sought to determine whether treatment results in measurable radiographic and biologic changes in estrogen receptor (ER)–positive DCIS. PATIENTS AND METHODS A phase II single-arm multicenter cooperative-group trial was conducted in postmenopausal patients diagnosed with ER-positive DCIS without invasion. Patients were treated with letrozole 2.5 mg per day for 6 months before surgery. Breast magnetic resonance imaging (MRI) was obtained at baseline, 3 months, and 6 months. The primary end point was change in 6-month MRI enhancement volume compared with baseline. RESULTS Overall, 79 patients were enrolled and 70 completed 6 months of letrozole. Of these, 67 patients had MRI data available for each timepoint. Baseline MRI volumes ranged from 0.004 to 26.3 cm3. Median reductions from baseline MRI volume (1.4 cm3) were 0.6 cm3 (61.0%) at 3 months ( P < .001) and 0.8 cm3 (71.7%) at 6 months ( P < .001). Consistent reductions were seen in median baseline ER H-score (228; median reduction, 15.0; P = .005), progesterone receptor H-score (15; median reduction, 85.0; P < .001), and Ki67 score (12%; median reduction, 6.3%; P = .007). Of the 59 patients who underwent surgery per study protocol, persistent DCIS remained in 50 patients (85%), invasive cancer was detected in six patients (10%), and no residual DCIS or invasive cancer was seen in nine patients (15%). CONCLUSIONS In a cohort of postmenopausal women with ER-positive DCIS, preoperative letrozole resulted in significant imaging and biomarker changes. These findings support future trials of extended endocrine therapy as primary nonoperative treatment of some DCIS.

This review reflects a collaboration between the American Registry of Pathology (the publisher of the Armed Forces Institute of Pathology Fascicles) and Annals of Diagnostic Pathology. It is part of a series of expert recommendations on topics encountered in daily practice. The authors, 4 pathologists with expertise in breast pathology and a breast surgeon with a clinical and research interest in lobular carcinoma in situ (LCIS), met by conference call in September 2019 to develop recommendations for evaluating and reporting LCIS. Herein, we summarize the diagnostic criteria of classic LCIS and LCIS subtypes according to the most recent WHO criteria, discuss how best to distinguish LCIS from ductal carcinoma in situ in problematic cases (including the uses and limitations of E-cadherin immunohistochemistry), and review outcome and management issues for patients with LCIS.

Angiosarcoma (AS) is the most frequent primary sarcoma of the breast but nevertheless remains uncommon, accounting for0.05% of breast malignancies. Secondary mammary AS arise following radiation therapy for breast cancer, in contrast to primary AS which occur sporadically. Essentially all show aggressive clinical behavior independent of histologic grade and most are treated by mastectomy. MYC amplification is frequently identified in radiation-induced AS but only rarely in primary mammary AS (PMAS). As a heterogeneous group, AS from various anatomic sites have been shown to harbor recurrent alterations in TP53, MAP kinase pathway genes, and genes involved in angiogenic signaling including KDR (VEGFR2) and PTPRB. In part due to its rarity, the pathogenesis of PMAS has not been fully characterized. In this study, we examined the clinical, pathologic, and genomic features of ten cases of PMAS, including one patient with bilateral disease. Recurrent genomic alterations were identified in KDR (70%), PIK3CA/PIK3R1 (70%), and PTPRB (30%), each at higher frequencies than reported in AS across all sites. Six tumors harbored a KDR p.T771R hotspot mutation, and all seven KDR-mutant cases showed evidence suggestive of biallelism (four with loss of heterozygosity and three with two aberrations). Of the seven tumors with PI3K alterations, six harbored pathogenic mutations other than in the canonical PIK3CA residues which are most frequent in breast cancer. Three AS were hypermutated (≥10 mutations/megabase (Mb)); hypermutation was seen concurrent with KDR or PIK3CA mutations. The patient with bilateral disease demonstrated shared alterations, indicative of contralateral metastasis. No MYC or TP53 aberrations were detected in this series. Immunohistochemistry for VEGFR2 was unable to discriminate between KDR-mutant tumors and benign vascular lesions of the breast. These findings highlight the underrecognized frequency of KDR and PIK3CA mutation in PMAS, and a significant subset with hypermutation, suggesting a pathogenesis distinct from other AS.

Pleomorphic (PLCIS) and florid (FLCIS) lobular carcinoma in situ are rare histologic variants of LCIS that are considered more aggressive than classic LCIS (CLCIS), but optimal treatment is controversial. The genetic drivers of these lesions and their clonal relationships to paired CLCIS and ILC have not been characterized. We used capture-based next-generation sequencing to profile 16 LCIS variants (ten PLCIS, six FLCIS), including paired synchronous ILC and CLCIS in 11 and nine cases, respectively. Recurrent pathogenic alterations included CDH1 (9/10 PLCIS, 6/6 FLCIS), PIK3CA (7/10 PLCIS, 2/6 FLCIS), ERBB2 (6/10 PLCIS, 2/6 FLCIS; six mutations, two amplifications), ERBB3 (1/10 PLCIS, 2/6 FLCIS), FOXA1 (4/10 PLCIS, 1/6 FLCIS), TP53 (3/10 PLCIS), and CCND1 (2/10 PLCIS, 1/6 FLCIS). Mutational profiles and mean copy number alterations (CNA) were similar between LCIS variants with and without ILC. Compared with ILC in The Cancer Genome Atlas (TCGA), PLCIS, FLCIS, and associated ILC were enriched for ERBB2 mutations, and PLCIS was enriched for TP53 and FOXA1 mutations. Shared pathogenic mutations and CNA were identified between the LCIS variant and ILC in all cases, and between CLCIS and the LCIS variant/ILC in 89%. CLCIS to PLCIS progression was associated with increased mean nonsynonymous mutations and additional pathogenic alterations and/or CNA in 80%. Mean nonsynonymous mutations and CNA were similar between PLCIS and ILC, although additional pathogenic mutations were associated with invasion in a subset (43%). FLCIS harbored additional clonal pathogenic mutations in only 1/3 cases, and these were not shared with ILC, which was genetically divergent. In another case, ILC was genetically more similar to CLCIS than FLCIS. The results highlight clonal relationships between PLCIS/FLCIS and CLCIS, and implicate PLCIS as a genetically advanced ILC precursor. Frequent ERBB2/ERBB3 alterations in PLCIS and FLCIS are consistent with more aggressive behavior and may have prognostic and therapeutic implications.

Malignant phyllodes tumors of the breast are poorly understood rare neoplasms with potential for aggressive behavior. Few efficacious treatment options exist for progressed or metastatic disease. The molecular features of malignant phyllodes tumors are poorly defined, and a deeper understanding of the genetics of these tumors may shed light on pathogenesis and progression and potentially identify novel treatment approaches. We sequenced 510 cancer-related genes in 10 malignant phyllodes tumors, including 5 tumors with liposarcomatous differentiation and 1 with myxoid chondrosarcoma-like differentiation. Intratumoral heterogeneity was assessed by sequencing two separate areas in 7 tumors, including non-heterologous and heterologous components of tumors with heterologous differentiation. Activating hotspot mutations in FGFR1 were identified in 2 tumors. Additional recurrently mutated genes included TERT promoter (6/10), TP53 (4/10), PIK3CA (3/10), MED12 (3/10), SETD2 (2/10) and KMT2D (2/10). Together, genomic aberrations in FGFR/EGFR PI-3 kinase and RAS pathways were identified in 8 (80%) tumors and included mutually exclusive and potentially actionable activating FGFR1, PIK3CA and BRAF V600E mutations, inactivating TSC2 mutation, EGFR amplification and PTEN loss. Seven (70%) malignant phyllodes tumors harbored TERT aberrations (six promoter mutations, one amplification). For comparison, TERT promoter mutations were identified by Sanger sequencing in 33% borderline (n=12) and no (0%, n=8) benign phyllodes tumors (P=0.391 and P=0.013 vs malignant tumors, respectively). Genetic features specific to liposarcoma, including CDK4/MDM2 amplification, were not identified. Copy number analysis revealed intratumoral heterogeneity and evidence for divergent tumor evolution in malignant phyllodes tumors with and without heterologous differentiation. Tumors with liposarcomatous differentiation revealed more chromosomal aberrations in non-heterologous components compared with liposarcomatous components. EGFR amplification was heterogeneous and present only in the non-heterologous component of one tumor with liposarcomatous differentiation. The results identify novel pathways involved in the pathogenesis of malignant phyllodes tumors, which significantly increase our understanding of tumor biology and have potential clinical impact.

SummaryInvasive lobular carcinoma (ILC) is the second most prevalent histologic subtype of invasive breast cancer. Here, we comprehensively profiled 817 breast tumors, including 127 ILC, 490 ductal (IDC), and 88 mixed IDC/ILC. Besides E-cadherin loss, the best known ILC genetic hallmark, we identified mutations targeting PTEN, TBX3, and FOXA1 as ILC enriched features. PTEN loss associated with increased AKT phosphorylation, which was highest in ILC among all breast cancer subtypes. Spatially clustered FOXA1 mutations correlated with increased FOXA1 expression and activity. Conversely, GATA3 mutations and high expression characterized luminal A IDC, suggesting differential modulation of ER activity in ILC and IDC. Proliferation and immune-related signatures determined three ILC transcriptional subtypes associated with survival differences. Mixed IDC/ILC cases were molecularly classified as ILC-like and IDC-like revealing no true hybrid features. This multidimensional molecular atlas sheds new light on the genetic bases of ILC and provides potential clinical options.

Importance Pathologic complete response (pCR) is a known prognostic biomarker for long-term outcomes. The I-SPY2 trial evaluated if the strength of this clinical association persists in the context of a phase 2 neoadjuvant platform trial. Objective To evaluate the association of pCR with event-free survival (EFS) and pCR with distant recurrence–free survival (DRFS) in subpopulations of women with high-risk operable breast cancer treated with standard therapy or one of several novel agents. Design, Setting, and Participants Multicenter platform trial of women with operable clinical stage 2 or 3 breast cancer with no prior surgery or systemic therapy for breast cancer; primary tumors were 2.5 cm or larger. Women with tumors that were ERBB2 negative/hormone receptor (HR) positive with low 70-gene assay score were excluded. Participants were adaptively randomized to one of several different investigational regimens or control therapy within molecular subtypes from March 2010 through 2016. The analysis included participants with follow-up data available as of February 26, 2019. Interventions Standard-of-care neoadjuvant therapy consisting of taxane treatment with or without (as control) one of several investigational agents or combinations followed by doxorubicin and cyclophosphamide. Main Outcomes and Measures Pathologic complete response and 3-year EFS and DRFS. Results Of the 950 participants (median [range] age, 49 [23-77] years), 330 (34.7%) achieved pCR. Three-year EFS and DRFS for patients who achieved pCR were both 95%. Hazard ratios for pCR vs non-pCR were 0.19 for EFS (95% CI, 0.12-0.31) and 0.21 for DRFS (95% CI, 0.13-0.34) and were similar across molecular subtypes, varying from 0.14 to 0.18 for EFS and 0.10 to 0.20 for DRFS. Conclusions and Relevance The 3-year outcomes from the I-SPY2 trial show that, regardless of subtype and/or treatment regimen, including 9 novel therapeutic combinations, achieving pCR after neoadjuvant therapy implies approximately an 80% reduction in recurrence rate. The goal of the I-SPY2 trial is to rapidly identify investigational therapies that may improve pCR when validated in a phase 3 confirmatory trial. Whether pCR is a validated surrogate in the sense that a therapy that improves pCR rate can be assumed to also improve long-term outcome requires further study. Trial Registration ClinicalTrials.gov Identifier:NCT01042379

BACKGROUND: Though mammographic density (MD) has been proposed as an intermediate marker of breast cancer risk, few studies have examined whether the associations between breast cancer risk factors and risk are mediated by MD, particularly by tumor characteristics. METHODS: Our study population included 3,392 cases (1,105 premenopausal) and 8,882 (3,192 premenopausal) controls from four case-control studies. For established risk factors, we estimated the percent of the total risk factor association with breast cancer that was mediated by percent MD (secondarily, by dense area and non-dense area) for invasive breast cancer as well as for subtypes defined by the estrogen receptor (ER+/ER−), progesterone receptor (PR+/PR−), and HER2 (HER2+/HER2−). Analyses were conducted separately in pre- and postmenopausal women. RESULTS: Positive associations between prior breast biopsy and risk of invasive breast cancer as well as all subtypes were partially mediated by percent MD in pre- and postmenopausal women (percent mediated=11–27%, p≤0.02). In postmenopausal women, nulliparity and hormone therapy use were positively associated with invasive, ER+, PR+, and HER2− breast cancer; percent MD partially mediated these associations (percent mediated≥31%, p≤0.02). Further, among postmenopausal women, percent MD partially mediated the positive association between later age at first birth and invasive as well as ER+ breast cancer (percent mediated=16%, p≤0.05). CONCLUSION: Percent MD partially mediated the associations between breast biopsy, nulliparity, age at first birth, and hormone therapy with risk of breast cancer, particularly among postmenopausal women, suggesting that these risk factors at least partially influence breast cancer risk through changes in breast tissue composition.

Background: Mammographic density (MD) is a strong breast cancer risk factor. We previously reported associations of percent mammographic density (PMD) with larger and node-positive tumors across all ages, and estrogen receptor (ER)–negative status among women ages Methods: Data were pooled from six studies including 4,095 breast cancers and 8,558 controls. DA and NDA were assessed from digitized film-screen mammograms and standardized across studies. Breast cancer odds by density phenotypes and age according to histopathologic characteristics and receptor status were calculated using polytomous logistic regression. Results: DA was associated with increased breast cancer risk [OR for quartiles: 0.65, 1.00 (Ref), 1.22, 1.55; Ptrend Conclusions: DA and NDA have differential associations with ER+ versus ER− tumors that vary by age. Impact: DA and NDA are important to consider when developing age- and subtype-specific risk models. Cancer Epidemiol Biomarkers Prev; 24(5); 798–809. ©2015 AACR.

Fibroepithelial lesions of the breast comprise a morphologically and biologically heterogeneous group of biphasic tumors with epithelial and stromal components that demonstrate widely variable clinical behavior. Fibroadenomas are common benign tumors with a number of histologic variants, most of which pose no diagnostic challenge. Cellular and juvenile fibroadenomas can have overlapping features with phyllodes tumors and should be recognized. Phyllodes tumors constitute a spectrum of lesions with varying clinical behavior and are graded as benign, borderline or malignant based on a set of histologic features according to recommendations by the World Health Organization (WHO). Recent developments have significantly expanded our understanding of the pathogenesis of fibroepithelial lesions, highlighting fibroadenomas as true neoplasms and underscoring a commonality with phyllodes tumors in the form of recurrent MED12 exon 2 mutations. In addition, sequencing studies have elucidated pathways associated with phyllodes tumor progression. Accurate diagnosis and grading of phyllodes tumors are important for patient management and prognosis, as grade broadly correlates with increasing local recurrence risk, and essentially only malignant tumors metastasize. However, classification of fibroepithelial lesions in many cases remains challenging on both core biopsy and excision specimens. A commonly encountered problem at the benign end of the spectrum is the distinction of benign phyllodes tumor from cellular fibroadenoma, which is largely due to the subjective nature of histologic features used in diagnosis and histologic overlap between lesions. Grading is further complicated by the requirement to integrate multiple subjective and ill-defined parameters. On the opposite end of the histologic spectrum, malignant phyllodes tumors must be distinguished from more common metaplastic carcinomas and from primary or metastatic sarcomas, which can be especially difficult in core biopsies. Immunohistochemistry can be useful in the differential diagnosis but should be interpreted with attention to caveats. This review provides an overview and update on the spectrum of fibroepithelial lesions, with special emphasis on common problems and practical issues in diagnosis.

Purpose: Several pathologic staging systems characterize residual tumor in patients undergoing neoadjuvant chemotherapy for breast cancer. Pathologic complete response (pCR) is now accepted by the Food and Drug Administration as an endpoint for granting accelerated drug approval. Two other systems of post-neoadjuvant pathologic tumor staging���residual cancer burden (RCB) and the American Joint Committee on Cancer post-neoadjuvant therapy staging system (yAJCC)���have been developed to characterize residual tumors when patients do not achieve pCR. The optimal system and the ways in which these systems complement each other have not been fully determined. Methods: Using data from the I-SPY 1 TRIAL, we compared pCR, RCB, and yAJCC as predictors of early recurrence-free survival (RFS) to identify ways to improve post-neoadjuvant pathologic evaluation. Results: Among 162 patients assessed, pCR identified patients at lowest risk of recurrence, while RCB and yAJCC identified patients at highest risk. Hormone-receptor (HR) and HER2 subtypes further improved risk prediction. Recursive partitioning indicated that triple-negative or HER2+ patients with yAJCC III or RCB 3 have the highest recurrence risk, with an RFS of 27%. Our analysis also highlighted discrepancies between RCB and yAJCC stratification: 31% of patients had discrepant RCB and yAJCC scores. We identified differential treatment of lymph node involvement and tumor cellularity as drivers of these discrepancies. Conclusions: These data indicate that there is benefit to reporting both RCB and yAJCC for patients in order to identify those at highest risk of relapse.

Secretory carcinomas of the breast are rare tumors with distinct histologic features, recurrent t(12;15)(p13;q25) translocation resulting in ETV6-NTRK3 gene fusion and indolent clinical behavior. Mammary analog secretory carcinomas arising in other sites are histopathologically similar to the breast tumors and also harbor ETV6-NTRK3 fusions. Breast secretory carcinomas are often triple (estrogen and progesterone receptor, HER2) negative with a basal-like immunophenotype. However, genomic studies are lacking, and whether these tumors share genetic features with other basal and/or triple negative breast cancers is unknown. Aside from shared ETV6-NTRK3 fusions, the genetic relatedness of secretory carcinomas arising in different sites is also uncertain. We immunoprofiled and sequenced 510 cancer-related genes in nine breast secretory carcinomas and six salivary gland mammary analog secretory carcinomas. Immunoprofiles of breast and salivary gland secretory carcinomas were similar. All the tumors showed strong diffuse MUC4 expression (n=15), and SOX10 was positive in all nine breast and in five out of six salivary gland tumors. All breast secretory carcinomas were triple negative or weakly ER-positive, and all tumors at both the sites expressed CK5/6 and/or EGFR, consistent with a basal-like phenotype. Sequencing revealed classic ETV6-NTRK3 fusion genes in all cases, including in carcinoma in situ of one breast tumor. Translocations were reciprocal and balanced in six out of nine breast and three out of six salivary gland tumors and were complex in three others. In contrast to most breast basal carcinomas, the mutational burden of secretory carcinomas was very low, and no additional pathogenic aberrations were identified in genes typically mutated in breast cancer. Five (56%) breast and two (33%) salivary gland tumors had simple genomes without copy number changes; the remainder had very few changes, averaging 1.3 per tumor. The ETV6-NTRK3 derivative chromosome was duplicated in one breast and one salivary gland tumor, and was the only copy number change in the latter. The findings highlight breast secretory carcinoma as a subtype more closely related to mammary analog secretory carcinoma than to basal/triple negative breast cancers of no special type. Lack of pathogenic mutations in common cancer-related genes suggests that ETV6-NTRK3 alone may suffice to drive these tumors and likely helps explain their indolent behavior.

We examined the associations of mammographic breast density with breast cancer risk by tumor aggressiveness and by menopausal status and current postmenopausal hormone therapy. This study included 2596 invasive breast cancer cases and 4059 controls selected from participants of four nested case–control studies within four established cohorts: the Mayo Mammography Health Study, the Nurses’ Health Study, Nurses’ Health Study II, and San Francisco Mammography Registry. Percent breast density (PD), absolute dense (DA), and non-dense areas (NDA) were assessed from digitized film-screen mammograms using a computer-assisted threshold technique and standardized across studies. We used polytomous logistic regression to quantify the associations of breast density with breast cancer risk by tumor aggressiveness (defined as presence of at least two of the following tumor characteristics: size ≥2 cm, grade 2/3, ER-negative status, or positive nodes), stratified by menopausal status and current hormone therapy. Overall, the positive association of PD and borderline inverse association of NDA with breast cancer risk was stronger in aggressive vs. non-aggressive tumors (≥51 vs. 11–25% OR 2.50, 95% CI 1.94–3.22 vs. OR 2.03, 95% CI 1.70–2.43, p-heterogeneity = 0.03; NDA 4th vs. 2nd quartile OR 0.54, 95% CI 0.41–0.70 vs. OR 0.71, 95% CI 0.59–0.85, p-heterogeneity = 0.07). However, there were no differences in the association of DA with breast cancer by aggressive status. In the stratified analysis, there was also evidence of a stronger association of PD and NDA with aggressive tumors among postmenopausal women and, in particular, current estrogen+progesterone users (≥51 vs. 11–25% OR 3.24, 95% CI 1.75–6.00 vs. OR 1.93, 95% CI 1.25–2.98, p-heterogeneity = 0.01; NDA 4th vs. 2nd quartile OR 0.43, 95% CI 0.21–0.85 vs. OR 0.56, 95% CI 0.35–0.89, p-heterogeneity = 0.01), even though the interaction was not significant. Our findings suggest that associations of mammographic density with breast cancer risk differ by tumor aggressiveness. While there was no strong evidence that these associations differed by menopausal status or hormone therapy, they did appear more prominent among current estrogen+progesterone users.

Extracellular matrix (ECM) stiffness induces focal adhesion assembly to drive malignant transformation and tumor metastasis. Nevertheless, how force alters focal adhesions to promote tumor progression remains unclear. Here, we explored the role of the focal adhesion protein vinculin, a force-activated mechanotransducer, in mammary epithelial tissue transformation and invasion. We found that ECM stiffness stabilizes the assembly of a vinculin–talin–actin scaffolding complex that facilitates PI3K-mediated phosphatidylinositol (3,4,5)-triphosphate phosphorylation. Using defined two- and three-dimensional matrices, a mouse model of mammary tumorigenesis with vinculin mutants, and a novel super resolution imaging approach, we established that ECM stiffness, per se, promotes the malignant progression of a mammary epithelium by activating and stabilizing vinculin and enhancing Akt signaling at focal adhesions. Our studies also revealed that vinculin strongly colocalizes with activated Akt at the invasive border of human breast tumors, where the ECM is stiffest, and we detected elevated mechanosignaling. Thus, ECM stiffness could induce tumor progression by promoting the assembly of signaling scaffolds, a conclusion underscored by the significant association we observed between highly expressed focal adhesion plaque proteins and malignant transformation across multiple types of solid cancer. See all articles in this Cancer Research section, “Physics in Cancer Research.” Cancer Res; 74(17); 4597–611. ©2014 AACR.

We evaluated genomic alterations and biomarker expression in 20 florid lobular carcinomas in situ using array-based comparative genomic hybridization and immunohistochemical analysis. The genetic characteristics of florid lobular carcinoma in situ were compared with 20 classic lobular carcinomas in situ and 21 pleomorphic lobular carcinomas in situ (which included 8 apocrine variants), from our previously published data performed on a similar array-based comparative genomic hybridization platform. All 20 florid lobular carcinoma in situ cases were E-cadherin negative, and 92% were positive for estrogen receptor. Cyclin D1 expression correlated significantly negatively with estrogen receptor expression and was higher in cases with cyclin D1 (CCND1) gene amplification. Compared with classic lobular carcinoma in situ, florid lobular carcinoma in situ displayed significantly more fraction genome alteration (mean, 0.109 versus 0.072; P=.007), fraction genome loss (mean, 0.06 versus 0.03; P=.007), numbers of breakpoints (mean, 11.55 versus 6.95; P=.002), numbers of chromosome with breakpoints (mean, 5.85 versus 3.8; P=.004), and higher numbers of amplifications (mean, 2.10 versus 0.25; P=.03). Interestingly, florid lobular carcinoma in situ had the same genetic complexity as apocrine pleomorphic lobular carcinoma in situ. Our study demonstrated that florid lobular carcinoma in situ shares the cytologic features, E-cadherin loss, and the lobular genetic signature of 1q gain and 16q loss found in classic lobular carcinoma in situ. However, this variant demonstrates more genomic alterations than classic lobular carcinoma in situ and shares the same genetic complexity as apocrine pleomorphic lobular carcinoma in situ. Our data support the conclusion that florid lobular carcinoma in situ is genetically more advanced compared with the indolent phenotype of classic lobular carcinoma in situ. This may explain the greater frequency of concurrent invasive carcinoma in florid lobular carcinoma in situ compared with classic lobular carcinoma in situ.

The 2013 CAP/ASCO HER2 Testing Guidelines Update modified HER2 FISH categories such that some cases with 'monosomy', 'co-amplification/polysomy', low-level increased HER2 signals or clustered heterogeneity now are considered amplified or equivocal. This study examines the frequency and clinico-pathologic characteristics of breast cancers with equivocal or 'non-classical' HER2 FISH results. Breast cancers (2001-2014) with HER2 FISH results, HER2 immunohistochemistry, ER, grade, and age from three institutions (Stanford, UCSF, UWMC) were collected. HER2 FISH was interpreted using the updated recommendations. Amplified cases with non-classical results were grouped into the following categories: (1) 'monosomy' (ratio ≥2.0, mean HER2/cell

Tumors are stiff and data suggest that the extracellular matrix stiffening that correlates with experimental mammary malignancy drives tumor invasion and metastasis. Nevertheless, the relationship between tissue and extracellular matrix stiffness and human breast cancer progression and aggression remains unclear. We undertook a biophysical and biochemical assessment of stromal-epithelial interactions in noninvasive, invasive and normal adjacent human breast tissue and in breast cancers of increasingly aggressive subtype. Our analysis revealed that human breast cancer transformation is accompanied by an incremental increase in collagen deposition and a progressive linearization and thickening of interstitial collagen. The linearization of collagen was visualized as an overall increase in tissue birefringence and was most striking at the invasive front of the tumor where the stiffness of the stroma and cellular mechanosignaling were the highest. Amongst breast cancer subtypes we found that the stroma at the invasive region of the more aggressive Basal-like and Her2 tumor subtypes was the most heterogeneous and the stiffest when compared to the less aggressive Luminal A and B subtypes. Intriguingly, we quantified the greatest number of infiltrating macrophages and the highest level of TGF beta signaling within the cells at the invasive front. We also established that stroma stiffness and the level of cellular TGF beta signaling positively correlated with each other and with the number of infiltrating tumor-activated, macrophages, which was highest in the more aggressive tumor subtypes. These findings indicate that human breast cancer progression and aggression, collagen linearization and stromal stiffening are linked and implicate tissue inflammation and TGF beta.

A clinically distinct subgroup of pure ductal carcinoma in situ presents as an extensive, high-grade lesion, which nevertheless lacks invasion. We sought to evaluate differences between those ductal carcinomas in situ presenting as large versus small lesions while controlling for high-grade, to determine whether there exist phenotypic and genetic differences between the 2 groups. Fifty-two cases of pure high-grade ductal carcinomas in situ were collected retrospectively, consisting of 27 large (>40 mm) and 25 small (

The clinical, pathologic, and molecular features of pleomorphic lobular carcinoma in situ (PLCIS) and the relationship of PLCIS to classic LCIS (CLCIS) are poorly defined. In this study, we analyzed 31 cases of PLCIS (13 apocrine and 18 nonapocrine subtypes) and compared the clinical, pathologic, immunophenotypic, and genetic characteristics of these cases with those of 24 cases of CLCIS. Biomarker expression was examined using immunostaining for E-cadherin, gross cystic disease fluid protein-15, estrogen, progesterone, androgen receptor, human epidermal growth factor receptor2, CK5/6, and Ki67. Array-based comparative genomic hybridization to assess the genomic alterations was performed using microdissected formalin-fixed paraffin-embedded samples. Patients with PLCIS presented with mammographic abnormalities. Histologically, the tumor cells were dyshesive and showed pleomorphic nuclei, and there was often associated necrosis and microcalcifications. All lesions were E-cadherin negative. Compared with CLCIS, PLCIS showed significantly higher Ki67 index, lower estrogen receptor and progesterone receptor expression, and higher incidence of HER2 gene amplification. The majority of PLCIS and CLCIS demonstrated loss of 16q and gain of 1q. Apocrine PLCIS had significantly more genomic alterations than CLCIS and nonapocrine PLCIS. Although lack of E-cadherin expression and the 16q loss and 1q gain-array-based comparative genomic hybridization pattern support a relationship to CLCIS, PLCIS has clinical, mammographic, histologic, immunophenotypic, and genetic features that distinguish it from CLCIS. The histologic features, biomarker profile, and genomic instability observed in PLCIS suggest a more aggressive phenotype than CLCIS. However, clinical follow-up studies will be required to define the natural history and most appropriate management of these lesions.

Lymphovascular invasion is an adverse prognostic factor in breast cancer. The lymphatic endothelial marker D2-40 has been shown to improve accuracy in detecting lymphovascular invasion. In addition to marking lymphatic endothelium, D2-40 has been cursorily noted to react with breast myoepithelium. The extent of this expression and the potential for misinterpreting in situ carcinoma as lymphovascular invasion because of D2-40-positive myoepithelium have not been formally addressed. The aim of this study was to determine the scope of breast myoepithelial expression of D2-40 and to identify problematic patterns of expression by in situ carcinoma that could be confused with lymphovascular invasion. We evaluated the distribution and intensity of D2-40 immunohistochemical expression in breast myoepithelium in normal breast (n = 50), proliferative fibrocystic changes (n = 10), ductal carcinoma in situ (n = 35), and lobular carcinoma in situ (n = 5). All cases of normal breast exhibited a variable degree of D2-40 expression by myoepithelium. The distribution was patchy and the intensity was less than that of the adjacent lymphatic endothelium. Larger ducts were more often positive than terminal ducts and lobules. D2-40 marked 77% of ductal carcinoma in situ cases and all lobular carcinoma in situ cases to a variable degree. Only a minority of involved ducts were reactive in each positive case; the intensity was weak to moderate. Although the tumor growth pattern generally enabled distinction of ductal carcinoma in situ from lymphovascular invasion, D2-40 myoepithelial expression in small ducts completely filled by solid-pattern ductal carcinoma in situ mimicked the pattern expected for lymphovascular invasion. Morphology of these myoepithelial cells was not diagnostically helpful as their compressed, stretched-out shape mimicked that of endothelium. Myoepithelial markers (p63 and smooth muscle myosin) confirmed each diagnosis of ductal carcinoma in situ. Lobular carcinoma in situ posed similar problems. The interpretation of D2-40 in the breast requires awareness that myoepithelium may also be immunoreactive. Solid-pattern ductal carcinoma in situ and lobular carcinoma in situ may be misinterpreted as lymphovascular invasion. We recommend that myoepithelial markers be used in conjunction with D2-40 to distinguish solid intralymphatic tumor emboli from solid pattern in situ carcinoma.

Hormone receptor status is an integral component of decision-making in breast cancer management. IHC4 score is an algorithm that combines hormone receptor, HER2, and Ki-67 status to provide a semiquantitative prognostic score for breast cancer. High accuracy and low interobserver variance are important to ensure the score is accurately calculated; however, few previous efforts have been made to measure or decrease interobserver variance. We developed a Web-based training tool, called "Score the Core" (STC) using tissue microarrays to train pathologists to visually score estrogen receptor (using the 300-point H score), progesterone receptor (percent positive), and Ki-67 (percent positive). STC used a reference score calculated from a reproducible manual counting method. Pathologists in the Athena Breast Health Network and pathology residents at associated institutions completed the exercise. By using STC, pathologists improved their estrogen receptor H score and progesterone receptor and Ki-67 proportion assessment and demonstrated a good correlation between pathologist and reference scores. In addition, we collected information about pathologist performance that allowed us to compare individual pathologists and measures of agreement. Pathologists' assessment of the proportion of positive cells was closer to the reference than their assessment of the relative intensity of positive cells. Careful training and assessment should be used to ensure the accuracy of breast biomarkers. This is particularly important as breast cancer diagnostics become increasingly quantitative and reproducible. Our training tool is a novel approach for pathologist training that can serve as an important component of ongoing quality assessment and can improve the accuracy of breast cancer prognostic biomarkers.

Purpose Magnetic resonance imaging (MRI) is an important tool for characterizing invasive breast cancer but has proven to be more challenging in the setting of ductal carcinoma in situ (DCIS). We investigated whether MRI features of DCIS reflect differences in biology and pathology. Patients and Methods Forty five of 100 patients with biopsy-proven DCIS who underwent MRI and had sufficient tissue to be characterized by pathologic (nuclear grade, presence of comedo necrosis, size, and density of disease) and immunohistochemical (IHC) findings (proliferation, Ki67; angiogenesis, CD34; and inflammation, CD68). Pathology and MRI features (enhancement patterns, distribution, size, and density) were analyzed using pairwise and canonical correlations. Results Histopathologic and IHC variables correlated with MRI features (r = 0.73). The correlation was largely due to size, density (by either MRI or pathology), and inflammation (P < .05). Most small focal masses were estrogen receptor-positive. MRI enhancement patterns that were clumped were more likely than heterogeneous patterns to be high-grade lesions. Homogenous lesions were large, high grade, and rich in macrophages. Presence of comedo necrosis and size could be distinguished on MRI (P < .05). MRI was most likely to over-represent the size of less dense, diffuse DCIS lesions. Conclusion The heterogeneous presentation of DCIS on MRI reflects underlying histopathologic differences.

Imaging patterns of benign proliferative processes often complicate the assessment of ductal carcinoma in situ (DCIS) by magnetic resonance imaging (MRI). We investigated the pathologic and biologic characteristics of false positive enhancement by breast MRI.DCIS (n = 45), benign (n = 5), and false-positive (MRI enhancement and nonmalignant pathology) (n = 10) cases were characterized by immunohistochemistry and MRI features.For DCIS cases, images that overestimated pathologic size had heterogeneous enhancement on MR, were estrogen receptor positive, and were low grade by pathology. False-positives had higher rates of proliferation, angiogenesis, and inflammation compared with benign tissue but lower values than DCIS. Benign proliferative processes accounted for all false-positive and size overestimated cases.Lesions that enhance on MRI have higher proliferation, angiogenesis, and inflammation compared with nonproliferative breast tissue. Benign proliferative processes often enhance on MRI and are difficult to differentiate from low-grade, ER+ DCIS lesions. False-positive MRI enhancement may reflect a spectrum of change within high-risk tissue.

Array-based comparative genomic hybridization (CGH) is a technique that allows genome wide screening of gains and losses in DNA copy number. In cases where multiple tumors are encountered, this genetic technique may prove useful in differentiating new primary tumors from recurrences. In this case report, we used array-based CGH to examine the genomic relationships among two leiomyosarcomas and two breast cancers in the same patient, three of which were diagnosed synchronously. Array-based CGH was performed on the four tumor samples using random prime amplified microdissected DNA. Samples were hybridized onto bacterial artificial chromosome arrays composed of approximately 2400 clones. Patterns of alterations within the tumors were compared and genetic alterations among the leiomyosarcomas and breast lesions were found. Overall, three distinct genetic profiles were observed. While the two leiomyosarcomas shared a similar pattern of genetic alterations, the two invasive breast lesions did not. The nearly identical pattern of genetic alterations belonging to the two metachronous leiomyosarcomas confirmed metastatic recurrence while the two different genetic profiles of the invasive ductal carcinomas suggest that the two lesions represented two distinct foci of multifocal disease rather than clonal extension of the primary tumor. We conclude that genetic analysis by array-based CGH can clearly elucidate the relationships between multiple tumors and may potentially serve as an important clinical tool.

It has been increasingly recognized that ductal carcinoma in situ (DCIS), lobular carcinoma in situ (LCIS) and invasive cancer of the breast are often closely associated with one another. However, the genomic relationship between these histologically distinct entities has not been well characterized. Refinements in high-resolution comparative genomic hybridization (CGH) techniques allow for a detailed comparison of genomic alterations in synchronously occurring tumors. The following case illustrates how array CGH may be used to better understand whether synchronous neoplasms share a common origin.

BACKGROUND Lobular carcinoma in situ (LCIS) of the breast is considered a marker for an increased risk of carcinoma in both breasts. However, the frequent association of LCIS with invasive lobular carcinoma (ILC) suggests a precursor-product relation. The possible genomic relation between synchronous LCIS and ILC was analyzed using the technique of array-based comparative genomic hybridization (CGH). METHODS Twenty-four samples from the University of California–San Francisco pathology archives that contained synchronous LCIS and ILC were identified. Array CGH was performed using random primer–amplified microdissected DNA. Samples were hybridized onto bacterial artificial chromosome arrays composed of approximately 2400 clones. Patterns of alterations within synchronous LCIS and ILC were compared. RESULTS A substantial proportion of the genome was altered in samples of both LCIS and ILC. The most frequent alterations were gain of 1q and loss of 16q, both of which usually occurred as whole-arm changes. Smaller regions of gain and loss were seen on other chromosome arms. Fourteen samples of LCIS were related more to their paired samples of ILC than to any other ILC, as demonstrated by a weighted similarity score. CONCLUSIONS LCIS and ILC are neoplastic lesions that demonstrate a range of genomic alterations. In the current study, the genetic relation between synchronous LCIS and ILC suggested clonality in a majority of the paired specimens. These data were consistent with a progression pathway from LCIS to ILC. The authors conclude that LCIS, which is known to be a marker for an environment that is permissive of neoplasia, may itself represent a precursor to invasive carcinoma. Cancer 2004. © 2004 American Cancer Society.

The widespread use of mammography has resulted in the detection of an increasing number of small invasive breast cancers, i.e. those that are 1cm and smaller. Patients with these small cancers generally have a low incidence of axillary lymph node metastases, and this has led some to question the routine use of axillary dissection in these patients. In addition, the prognosis of these patients is generally favorable, and the routine use of adjuvant systemic therapy is difficult to justify. Nonetheless, some patients with these small invasive cancers will have axillary nodal involvement and/or develop metastatic disease. The identification of this prognostically unfavorable subset of patients within this otherwise favorable group is an important goal of clinical research. In this article, we review the available literature on prognostic factors for patients with breast cancers 1cm and smaller to help determine which of these features might be of value in the identification of patients at risk for axillary lymph node involvement and/or metastatic disease.

Tissue mechanics regulate development and homeostasis and are consistently modified in tumor progression. Nevertheless, the fundamental molecular mechanisms through which altered mechanics regulate tissue behavior and the clinical relevance of these changes remain unclear. We demonstrate that increased matrix stiffness modulates microRNA expression to drive tumor progression through integrin activation of β-catenin and MYC. Specifically, in human and mouse tissue, increased matrix stiffness induced miR-18a to reduce levels of the tumor suppressor phosphatase and tensin homolog (PTEN), both directly and indirectly by decreasing levels of homeobox A9 (HOXA9). Clinically, extracellular matrix stiffness correlated directly and significantly with miR-18a expression in human breast tumor biopsies. miR-18a expression was highest in basal-like breast cancers in which PTEN and HOXA9 levels were lowest, and high miR-18a expression predicted poor prognosis in patients with luminal breast cancers. Our findings identify a mechanically regulated microRNA circuit that can promote malignancy and suggest potential prognostic roles for HOXA9 and miR-18a levels in stratifying patients with luminal breast cancers. © 2014 Nature America, Inc. All rights reserved.

Introduction Understanding whether mammographic density (MD) is associated with all breast tumor subtypes and whether the strength of association varies by age is important for utilizing MD in risk models. Methods Data were pooled from six studies including 3414 women with breast cancer and 7199 without who underwent screening mammography. Percent MD was assessed from digitized film-screen mammograms using a computer-assisted threshold technique. We used polytomous logistic regression to calculate breast cancer odds according to tumor type, histopathological characteristics, and receptor (estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor (HER2)) status by age (51%) versus average density (11-25%). Women ages 2.1 cm) versus small tumors and positive versus negative lymph node status (P’s

FOXP3-expressing T regulatory lymphocytes (Tregs) have been described as putative mediators of immune tolerance, and thus facilitators of tumor growth. When found in association with various malignancies, Tregs are generally markers of poor clinical outcome. However, it is unknown whether they are also associated with cancer progression. We evaluated quantitative FOXP3 expression in lymphocytes as well as in epithelial cells in a set of thirty-two breast tumors with synchronous normal epithelium, ductal carcinoma in situ (DCIS), and invasive ductal carcinoma (IDC) components. Tumors were stained for FOXP3 and CD3 expression and Tregs quantified by determining the ratio of colocalized FOXP3 and CD3 relative to 1) total CD3-expressing lymphocytes and 2) to FOXP3-expressing epithelial cells. The median proportion of FOXP3-expressing CD3 cells significantly increased with malignant progression from normal to DCIS to IDC components (0.005, 0.019 and 0.030, respectively; p ≤ 0.0001 for normal vs. IDC and p = 0.004 for DCIS vs. IDC). The median intensity of epithelial FOXP3 expression was also increased with invasive progression and most markedly augmented between normal and DCIS components (0.130 vs. 0.175, p ≤ 0.0001). Both Treg infiltration and epithelial FOXP3 expression were higher in grade 3 vs. grade 1 tumors (p = 0.014 for Tregs, p = 0.038 for epithelial FOXP3), but did not vary significantly with hormone receptor status, size of invasive tumor, lymph node status, or disease stage. Notably, Treg infiltration significantly correlated with epithelial up-regulation of FOXP3 expression (p = 0.013 for normal, p = 0.001 for IDC). These findings implicate both Treg infiltration and up-regulated epithelial FOXP3 expression in breast cancer progression.

Purpose Neoadjuvant chemotherapy for breast cancer provides critical information about tumor response; how best to leverage this for predicting recurrence-free survival (RFS) is not established. The I-SPY 1 TRIAL (Investigation of Serial Studies to Predict Your Therapeutic Response With Imaging and Molecular Analysis) was a multicenter breast cancer study integrating clinical, imaging, and genomic data to evaluate pathologic response, RFS, and their relationship and predictability based on tumor biomarkers. Patients and Methods Eligible patients had tumors ≥ 3 cm and received neoadjuvant chemotherapy. We determined associations between pathologic complete response (pCR; defined as the absence of invasive cancer in breast and nodes) and RFS, overall and within receptor subsets. Results In 221 evaluable patients (median tumor size, 6.0 cm; median age, 49 years; 91% classified as poor risk on the basis of the 70-gene prognosis profile), 41% were hormone receptor (HR) negative, and 31% were human epidermal growth factor receptor 2 (HER2) positive. For 190 patients treated without neoadjuvant trastuzumab, pCR was highest for HR-negative/HER2-positive patients (45%) and lowest for HR-positive/HER2-negative patients (9%). Achieving pCR predicted favorable RFS. For 172 patients treated without trastuzumab, the hazard ratio for RFS of pCR versus no pCR was 0.29 (95% CI, 0.07 to 0.82). pCR was more predictive of RFS by multivariate analysis when subtype was taken into account, and point estimates of hazard ratios within the HR-positive/HER2-negative (hazard ratio, 0.00; 95% CI, 0.00 to 0.93), HR-negative/HER2-negative (hazard ratio, 0.25; 95% CI, 0.04 to 0.97), and HER2-positive (hazard ratio, 0.14; 95% CI, 0.01 to 1.0) subtypes are lower. Ki67 further improved the prediction of pCR within subsets. Conclusion In this biologically high-risk group, pCR differs by receptor subset. pCR is more highly predictive of RFS within every established receptor subset than overall, demonstrating that the extent of outcome advantage conferred by pCR is specific to tumor biology.

Although high mammographic density is considered one of the strongest risk factors for invasive breast cancer, the genes involved in modulating this clinical feature are unknown. Tissues of high mammographic density share key histologic features with stromal components within malignant lesions of tumor tissues, specifically low adipocyte and high extracellular matrix (ECM) content. We show that CD36, a transmembrane receptor that coordinately modulates multiple protumorigenic phenotypes, including adipocyte differentiation, angiogenesis, cell–ECM interactions, and immune signaling, is greatly repressed in multiple cell types of disease-free stroma associated with high mammographic density and tumor stroma. Using both in vitro and in vivo assays, we show that CD36 repression is necessary and sufficient to recapitulate the above-mentioned phenotypes observed in high mammographic density and tumor tissues. Consistent with a functional role for this coordinated program in tumorigenesis, we observe that clinical outcomes are strongly associated with CD36 expression. Significance: CD36 simultaneously controls adipocyte content and matrix accumulation and is coordinately repressed in multiple cell types within tumor and high mammographic density stroma, suggesting that activation of this stromal program is an early event in tumorigenesis. Levels of CD36 and extent of mammographic density are both modifiable factors that provide potential for intervention. Cancer Discov; 2(9); 826–39. ©2012 AACR. Read the Commentary on this article by DeClerck, p. 772. This article is highlighted in the In This Issue feature, p. 753.

In animal and laboratory models, cancer-associated stroma, or elements of the supporting tissue surrounding a primary tumor, has been shown to be necessary for tumor evolution and progression. However, little is understood or studied regarding the properties of intact stroma in human cancer in vivo. In addition, for breast cancer patients, the optimal volume of local tissue to treat surrounding a primary tumor is not clear. Here, we performed an interdisciplinary study of normal-appearing breast tissue using breast magnetic resonance imaging (MRI), correlative histology and array comparative genomic hybridization to identify a cancer-associated stroma in humans. Using a novel technique for segmenting breast fibroglandular tissue, quantifiable topographic percent enhancement mapping of the stroma surrounding invasive breast cancer was found to be significantly elevated within 2 cm of the tumor edge. This region was also found to harbor increased microvessel density, and genomic changes that were closely associated with host normal breast tissue. These findings indicate that a cancer-associated stroma may be identified and characterized in human breast cancer using non-invasive imaging techniques. Identification of a cancer-associated stroma may be further developed to help guide local therapy to reduce recurrence and morbidity in breast cancer patients.

Purpose: Excess histone deacetylase (HDAC) activity can induce hypoacetylation of histone and nonhistone protein substrates, altering gene expression patterns and cell behavior potentially associated with malignant transformation. However, HDAC expression and protein acetylation have not been studied in the context of breast cancer progression. Experimental Design: We assessed expression levels of acetylated histone H4 (ac-H4), ac-H4K12, ac-tubulin, HDAC1, HDAC2, and HDAC6 in 22 reduction mammoplasties and in 58 specimens with synchronous normal epithelium, ductal carcinoma in situ (DCIS), and invasive ductal carcinoma (IDC) components. Differences among groups were tested for significance using nonparametric tests. Results: From normal epithelium to DCIS, there was a marked reduction in histone acetylation (P < 0.0001). Most cases showed similar levels of acetylation in DCIS and IDC, although some showed further reduction of ac-H4 and ac-H4K12 from DCIS to IDC. Expression of HDAC1, HDAC2, and HDAC6 was also significantly reduced but by a smaller magnitude. Greater reductions of H4 acetylation and HDAC1 levels were observed from normal to DCIS in estrogen receptor–negative compared with estrogen receptor–positive, and in high-grade compared with non–high-grade tumors. Conclusion: Overall, there was a global pattern of hypoacetylation associated with progression from normal to DCIS to IDC. These findings suggest that the reversal of this hypoacetylation in DCIS and IDC could be an early measure of HDAC inhibitor activity.

Neoadjuvant chemotherapy is standard of care for patients with locally advanced breast cancer. Patients who achieve a pathologic complete response have a more favorable outcome than those who do not; however, a standard system for classifying residual disease has not been adopted. Various definitions of complete response exist, some of which allow for minimal residual invasive or in situ carcinoma. The pattern of residual carcinoma restricted to lymphatic spaces without stromal invasion, herein called pure intralymphatic carcinoma, has not been well addressed. Neither has the pattern of minimal residual stromal invasive cancer accompanied by an extensive intralymphatic component, herein called predominantly pure intralymphatic carcinoma. We report the incidence, clinicopathologic features, and clinical significance of pure and predominantly pure intralymphatic carcinoma in a cohort of 146 neoadjuvant-treated breast cancer patients. We also evaluate the use of the immunohistochemical lymphatic marker D2-40 in these tissues exposed to neoadjuvant chemotherapy. Six patients (4%) had residual pure intralymphatic carcinoma. No gross abnormalities were present in the mastectomy specimens except for 1 case that had a discrete mass, corresponding to residual in situ carcinoma. Residual intralymphatic tumor size ranged from 0.2 to 6 cm. All but one had residual positive lymph nodes. Residual predominantly pure intralymphatic carcinoma was found in 5/146 (4%) patients. A discrete gross mass was observed in 3/5 specimens. Whereas residual stromal invasive carcinoma ranged in size from 0.1 to 1.8 cm, the intralymphatic component ranged from 6 to 9.3 cm. All had residual positive lymph nodes. D2-40 adequately marked lymphatic endothelium in all cases tested. Death occurred in 6/11 (55%) versus 17/135 (13%) patients with or without pure/predominantly pure intralymphatic carcinoma, respectively. After controlling for tumor stage, the presence of either of these residual intralymphatic patterns was associated with a 3-fold increase in death (Cox proportional hazards ratio=3.59, 95% confidence interval, 1.29, 9.99, P=0.014). Elevated risk for disease progression was also observed but this was not statistically significant. We conclude that pure/predominantly pure intralymphatic carcinoma is a clinically significant pattern of residual disease. This may be an underrecognized pattern because of the discordance between gross and microscopic findings and because of challenges in diagnosing intralymphatic carcinoma. D2-40 immunostaining is useful in this setting. Current staging criteria should be clarified to define whether extensive intralymphatic tumor should be incorporated in tumor stage assignment.

Summary Approximately 15%–30% of women diagnosed with ductal carcinoma in situ (DCIS) develop a subsequent tumor event within 10 years after surgical lumpectomy. To date, little is known about the molecular pathways that confer this differential risk for developing subsequent disease. In this study, we demonstrate that expression of biomarkers indicative of an abrogated response to cellular stress predicts DCIS with worse outcome and is a defining characteristic of basal-like invasive tumors. Mechanistic studies identify the Rb pathway as a key regulator of this response. Conversely, biomarkers indicative of an intact response to cellular stress are strongly associated with a disease-free prognosis. Assessment of these biomarkers in DCIS begins to allow prediction of tumor formation years before it actually occurs.

Aberrant microenvironments and loss of balance in cell-extracellular matrix signaling are associated with breast cancer invasion, metastasis, and resistance to therapy. We have recently shown that increased β1 integrin signaling is involved in malignant progression and that inhibitory antibody to β1 integrin leads to selective apoptosis and decreased proliferation in three-dimensional cultures and in xenograft models of breast cancer in vivo. To investigate the clinical importance of these findings, in the present study we examined the expression of β1 integrin and extracellular β1 integrin ligands fibronectin and laminin-1 in a cohort of 249 breast cancer patients who had a median follow-up of 8.4 years. Among the 149 scorable cases, the highest β1 integrin intensity score (3+ versus 0–2+) was associated with significantly decreased 10-year overall survival of 48% versus 71% (P < 0.03) and decreased disease-free survival of 50% versus 80% (P < 0.05). Importantly, high fibronectin expression was associated with decreased overall and disease-free survival on univariate analysis (P < 0.04) and β1 integrin intensity score was significantly correlated with fibronectin expression (Kendall's tau-b = 0.19; P = 0.03). In a multivariate Cox proportional hazards model, β1 integrin intensity score remained a significant independent predictor of overall survival [hazard ratio (HR), 1.69; 95% confidence interval (95% CI), 1.19–2.38; P < 0.003] and disease-free survival (HR, 1.87; 95% CI, 1.21–2.88; P < 0.005). These findings show that β1 integrin expression has potential prognostic value in invasive breast cancer and that coexpression of fibronectin may help identify patients with more aggressive tumors who may benefit from targeted therapy. [Cancer Res 2007;67(2):659–64]