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Mycobacterial spindle cell pseudotumors (MSPs) are a rare and diagnostically challenging manifestation of non-tuberculous mycobacterial (NTM) infections. Proper recognition of these pseudotumors is important because they are treatable and benign. In this study, we evaluated the morphologic patterns of MSPs to improve their pathologic identification. Clinical and morphologic features of 14 MSPs were analyzed. Histologic factors evaluated included the architectural growth pattern of spindled or epithelioid macrophages, granulomas and their location within the lesion, neutrophilic microabscesses, multinucleated giant cells, necrosis, and effacement of background tissue. The composition of inflammatory infiltrates, organism density by acid-fast staining, and stromal changes were also assessed. In addition, 8 of 14 cases underwent molecular microbiology identification by a clinical amplicon-sequencing assay for non-tuberculous mycobacteria. MSP sites included 2 bowel, 10 lymph nodes, 1 liver, and 1 extremity. Cases with available clinical history (n=10) all occurred in immunocompromised patients. All demonstrated effacement of normal structures with spindled cells arranged in a storiform or fascicular architectural pattern. In addition, all cases showed lymphocytic inflammation, with prominent concurrent neutrophilic inflammation in 50% (7/14) of cases. Other morphologic findings included foamy histiocytes (64%, 9/14), peripherally situated granulomas (21%, 3/14), and neutrophilic microabscesses (21%, 3/14). All tested cases were positive for NTM by PCR methods. Mycobacterium aviumwas the most commonly isolated pathogen (6/8). Mycobacterial spindle cell pseudotumors show predominantly spindled morphology that may be mistaken as a neoplasm. Surgical pathologists who evaluate lymph nodes, soft tissue, and gastrointestinal tissues should be aware of this spindled tumefactive phenomenon in the setting of immunocompromised patients. Recognition of key morphologic features of neutrophilic inflammation, peripheral granulomas, or foamy histiocytes within a spindled lesion can help guide the pathologist to a correct diagnosis of an inflammatory process secondary to infection rather than a spindle cell neoplasm. Accurate diagnosis to facilitate appropriate antimicrobial and/or surgical therapy requires a comprehensive evaluation combining clinical, histopathologic, and microbiological findings.

Microsecretory adenocarcinoma (MSA) of the salivary gland is a new entity recently added to the World Health Organization Classification of Head and Neck Tumors. This tumor is characterized by a recurrent MEF2C-SS18translocation. We present a nodular tumor confined to the dermis of the ear canal of a 44-year-old patient, which demonstrated classic histopathologic features and molecular alteration of MSA. Specifically, the tumor was composed of numerous tubules and microcysts filled with abundant basophilic mucinous secretion and associated with a fibromyxoid stroma. The tumor cells were diffusely positive for CK7 and SOX10 and variably positive for S100 and p63. Breakapart fluorescence in situ hybridization for SS18confirmed rearrangement of this gene. Together, these findings support a primary cutaneous MSA, presumably arising from ceruminous glands of the ear canal. Based on current knowledge of its salivary gland counterpart, cutaneous MSA is expected to be locally invasive but unlikely to recur or metastasize on complete excision.

Objectives: Phosphaturic mesenchymal tumor (PMT) is a rare, polymorphous neoplasm with a highly variable presentation and natural history and unpredictable clinical course. The primary objective was to describe our clinical experience with and management of 4 markedly different cases of sinonasal and skull base PMT.Methods: A retrospective case series with chart review, and relevant literature review, was performed at a tertiary academic medical center between 1998 and 2020. Adult patients treated for PMTs of the sinonasal area and skull base were included. Our main outcome measures included postoperative laboratory findings and radiological evidence of disease remission.Results: Four patients (2 Males, 2 Females; Mean Age: 63.5 years) with PMTs of the skull base have been managed at our institution since 1998. Patient presentations varied, ranging from severe phosphorus wasting and osteoporosis to symptoms secondary to mass effect, including nasal obstruction and rhinorrhea. All 4 patients were eventually found to have elevated levels of fibroblast growth factor 23. Tumors were located in the sinonasal area (right frontal sinus, right ethmoid sinus, and right nasal cavity, respectively) in 3 patients and in the lateral skull base (right jugular foramen) in 1 patient. All 4 patients underwent complete surgical resection of their tumors. PMT tissue pathology was confirmed in all cases. Gross total resection was achieved in all patients. There was no chemical or radiological evidence of disease recurrence in any patients at follow-up.Conclusions: The presentation of skull base PMT is variable, and it may mimic other mass pathologies of the head and neck. Complete surgical resection with negative margins is potentially curative.

Secretory carcinoma (SC), previously known as mammary analogue secretory carcinoma, is a rare salivary gland neoplasm that typically presents as a slow-growing painless lesion in the head and neck. SC occurs mainly in adults but has been described in children with the youngest reported patient diagnosed at five years of age. In children the gender distribution has been reported as female to male ratio of 1:1.2. SC is generally considered a low-grade malignancy with characteristic morphological features and immunological profile. SC also harbors ETV6-NTRK3 fusion (t(12;15)(p13:q25)). Surgical resection with or without lymph node dissection is the standard treatment, with generally favorable clinical outcomes. Here we present a single institution case series of six patients (ages 9-21) with SC and a review of the previously described pediatric cases. Our small series showed male predominance in pediatric patients with predominantly low-grade and stage tumors. All cases underwent complete surgical resections and when follow up is available there was no evidence of recurrences or metastases. To the best of our knowledge, this is the only SC case series comprised exclusively of pediatric and youth patients.

Sinonasal papillomas are benign epithelial tumors of the sinonasal tract that are associated with a synchronous or metachronous sinonasal carcinoma in a subset of cases. Our group recently identified mutually exclusive EGFRmutations and human papillomavirus (HPV) infection in inverted sinonasal papillomas and frequent KRASmutations in oncocytic sinonasal papillomas. We also demonstrated concordant mutational and HPV infection status in sinonasal papilloma-associated sinonasal carcinomas, confirming a clonal relationship between these tumors. Despite our emerging understanding of the oncogenic mechanisms driving formation of sinonasal papillomas, little is currently known about the molecular mechanisms of malignant progression to sinonasal carcinoma. In the present study, we utilized targeted next-generation DNA sequencing to characterize the molecular landscape of a large cohort of sinonasal papilloma-associated sinonasal carcinomas. As expected, EGFRor KRASmutations were present in the vast majority of tumors. In addition, highly recurrent TP53mutations, CDKN2Amutations, and/or CDKN2Acopy-number losses were detected; overall, nearly all tumors (n= 28/29; 96.6%) harbored at least one TP53or CDKN2Aalteration. TERTcopy-number gains also occurred frequently (27.6%); however, no TERTpromoter mutations were identified. Other recurrent molecular alterations included NFE2L2and PIK3CAmutations and SOX2, CCND1, MYC, FGFR1, and EGFRcopy-number gains. Importantly, TP53mutations and CDKN2Aalterations were not detected in matched sinonasal papillomas, suggesting that these molecular events are associated with malignant transformation. Compared to aerodigestive tract squamous cell carcinomas from The Cancer Genome Atlas (TCGA) project, sinonasal papilloma-associated sinonasal carcinomas have a distinct molecular phenotype, including more frequent EGFR, KRAS, and CDKN2Amutations, TERTcopy-number gains, and low-risk human papillomavirus (HPV) infection. These findings shed light on the molecular mechanisms of malignant progression of sinonasal papillomas and may have important diagnostic and therapeutic implications for patients with advanced sinonasal cancer.

The eighth edition of the American Joint Committee on Cancer (AJCC) Staging Manual attempts to address ambiguity in the pT category assignment for colon cancer from prior editions. Despite modifications, the distinction between the pT3 and pT4a categories continues to be a source of diagnostic confusion. In this study, we assessed interobserver agreement among pathologists from different institutions in the application of AJCC eighth edition criteria for categorizing deeply invasive colonic adenocarcinomas. We identified morphologic patterns that produce diagnostic confusion. We assessed 47 colon cancers that closely approached the serosal surface. Six pathologists with interest in gastrointestinal pathology and 4 focused in other subspecialties classified each case as pT3 or pT4a, based on examination of low-magnification and high-magnification images of the most deeply invasive area. Interobserver agreement was assessed using Fleiss’ κ. Cases displayed 3 morphologic patterns at the advancing tumor edge, namely, (1) continuous invasion through an inflammatory focus, (2) pushing border, and (3) infiltrative glands and cell clusters with serosal reaction. Gastrointestinal pathologists achieved slight (κ=0.21) or moderate (κ=0.46) and (κ=0.51) agreement in each category, whereas agreement among nongastrointestinal pathologist was fair (0.31) and (0.39), or moderate (0.57) for each category, respectively. In 10 (21%) cases, the distinction between pT3 and pT4a would have changed the overall clinical stage. We conclude that histologic criteria for serosal penetration is a persistent source of diagnostic ambiguity for gastrointestinal and general pathologists in the pT categorization of colon cancers. Clarification of these criteria will help ensure uniform reporting of pathologic and clinical stage.

IMPORTANCE: Biomarkers that reflect prognosis and cellular immunity in patients with head and neck squamous cell carcinoma (HNSCC) are a prerequisite for improving individualized treatment that limits the intensity and morbidity of conventional treatment and may be useful in the introduction of new immunotherapy regimens. OBJECTIVE: To determine if specific classes of tumor-infiltrating lymphocytes (TILs) in pretreatment biopsy specimens have prognostic value for outcomes in a large training and validation cohort of patients with HNSCC. DESIGN, SETTING, AND PARTICIPANTS: In this prospective, epidemiologic study with a median follow-up of 47.5 months, in 464 previously untreated patients with available tissue for construction of tissue microarray, HNSCC disease sites included oral cavity (228), oropharynx (147), larynx (74), and hypopharynx (15). The training cohort consisted of 241 patients and the validation cohort consisted of 223 patients. Overall tumor stage was I (55), II (69), III (71), or IV (269). Patients were enrolled between November 2008 to October 2014. Data were analyzed between October 2018 to April 2019. MAIN OUTCOMES AND MEASURES: Semiquantitative levels of CD4, CD8, and FoxP3 lymphocytes were assessed by immunohistologic analysis and correlations with clinical prognostic factors, initial treatment modality, and overall survival (OS) and disease-specific (DSS) survival were determined. A principal component analysis was performed to generate a combined TIL-weighted sum score (TILws). RESULTS: Of the 464 participants, 135 (29%) were women; mean (SD) age was 61.1 (11.8) years. Higher CD8 counts were associated with improved OS in both training and validation sets (HR, 0.94; 95% CI, 0.90-0.98; and HR, 0.97; 95% CI, 0.95-0.99, respectively). Higher TILws levels were associated with improved OS and DSS in both the training set (HR, 0.91; 95% CI, 0.86-0.96; and HR, 0.93; 95% CI, 0.87-0.99, respectively) and validation set (HR, 0.96; 95% CI, 0.93-0.99; and HR, 0.94; 95% CI, 0.89-0.99, respectively). A multivariable Cox model controlling for batch, age, clinical stage, disease site, comorbidities, HPV status, and smoking, showed that higher TILws levels were associated with improved OS and DSS (HR, 0.94; 95% CI, 0.92-0.97; and HR, 0.94; 95% CI, 0.90-0.98, respectively). When grouped by treatment (surgery vs chemoradiation) and tested for interaction, treatment was found to be an effect modifier for CD4 levels and OS. Low CD4 levels were showed greater association with decreased survival in the chemoradiation cohort than the surgery cohort. CONCLUSIONS AND RELEVANCE: The findings from this large cohort study suggest that levels of TILs are an independent prognostic factor in patients with HNSCC. Subsets of TILs and combined TIL scores may be clinically useful predictive and prognostic factors.

In recent years, a novel small round cell sarcoma harboring EWSR1-NFATC2translocation with immunomorphologic overlap with Ewing sarcoma (ES), myoepithelial tumors, and extraskeletal myxoid chondrosarcoma has emerged. There has not been a case series devoted to describing its detailed clinicopathologic and immunohistochemical characteristics. Six sarcomas harboring EWSR1-NFATC2fusion transcripts by reverse transcription polymerase chain reaction and amplification of the fusion gene by fluorescence in situ hybridization were identified. The patients were 5 adult men and 1 adult woman. Three were primary bone tumors of the radius and 3 were primary soft tissue tumors. Most tumors showed monomorphic round to epithelioid cells in anastomosing cords and abundant myxohyaline to collagenous extracellular matrix. Two tumors had large areas of a solid, matrix-poor histomorphology. All tumors stained for CD99 and NKX2.2; while EMA, dot-like cytokeratin, and focal WT-1 and SMA were present in some tumors. All but 1 tumor showed poor histologic and radiologic responses to neoadjuvant ES-specific chemotherapy. Local or distant recurrences happened in 4 cases. EWSR1-NFATC2sarcoma is a novel translocation-associated sarcoma. It presents as either a primary bone or soft tissue tumor, usually exhibits distinctive histopathologic features, and has predilection for long bones of adult men. It consistently shows recurrent fusion gene amplification readily detectable by EWSR1breakapart fluorescence in situ hybridization, which serves as a diagnostic surrogate. It has potential for local and distant recurrence and histologic progression, and is resistant to Ewing sarcoma-specific chemotherapy.

Lymphovascular invasion (LVI) of testicular germ cell tumors (GCT) is an important stage-determining variable in the evaluation of radical orchiectomy specimens. ERG endothelial cell expression, as detected by immunohistochemistry (IHC), robustly highlights lymphovascular spaces, and thus, we sought to assess the utility of ERG IHC for evaluation of GCT LVI. Hematoxylin and eosin (H&E) slides from a retrospective cohort of 25 GCT radical orchiectomy specimens (emanating from a parent cohort of 159 radical orchiectomy GCT cases identified between 2003 and 2013) were reviewed, and sections with foci of positive or equivocal LVI were identified. ERG IHC was performed on sections off the surface of corresponding paraffin tissue blocks. All foci were then rescored as positive, equivocal, or negative for LVI based on ERG endothelial cell expression. Twenty-three and 13 foci were positive or equivocal for LVI by H&E staining, respectively. Among the H&E positive LVI foci, 20 (87%) were ERG IHC positive, whereas of the H&E equivocal LVI foci, 5 (38%) were ERG IHC positive, 3 (23%) were ERG IHC negative, and 2 (15%) were ERG IHC equivocal; all other foci were lost for evaluation. Overall, ERG IHC helped resolve the LVI status of 61% of foci deemed equivocal for LVI by H&E staining only. Although ERG IHC is useful in confirming definitive LVI status in a subset of GCT cases, the overall clinical impact of ERG IHC is limited for H&E equivocal LVI foci in this specific retrospective patient cohort. Overall, in carefully selected clinical scenarios, these data suggest a supportive role for ERG IHC in evaluation of GCT LVI in radical orchiectomy specimens.

Dermatofibrosarcoma protuberans (DFSP) of the distal extremities and acral sites are extremely rare and incompletely characterized. Twenty-seven DFSP occurring in these sites were retrieved from our collective archives and reevaluated. Tumors occurred in 16 males and 11 females. Median age at presentation was 42.5 years (range, 7 to 78 y). Lesions involved the foot (18 with 6 in the toes and 2 on the plantar foot), distal ankle (4), hand (4 with 2 in the thumbs), and wrist (1). All cases showed predominantly classic DFSP morphology and were diffusely CD34 positive. Myxoid change, melanin pigmented, and giant cell fibroblastoma foci were each present in 1 case, respectively. Fibrosarcomatous change was present in 3 cases. Fluorescent in situ hybridization demonstrated PDGFBgene rearrangement in 9 of 10 tested cases. Clinical follow-up was available in 21 cases (median, 36.1 mo; range, 1 to 152 mo) and revealed 4 local recurrences. Four patients underwent digital amputation for unresectable recurrent disease. An additional patient underwent multiple resections with positive margins and elected to receive imatinib mesylate therapy. After a 2-year course, the patient has no evidence of residual disease (40 mo). No metastases were documented in any of the cases studied. The natural history of DFSP of distal extremities and acral sites is similar to that of its counterparts elsewhere. A high index of suspicion, careful morphologic examination for key histologic features of DFSP, and in selected cases, molecular studies to identify the pathognomonic COL1A1-PDGFBgene fusion should facilitate the distinction of these rare, locally aggressive neoplasms from morphologic mimics that may arise in distal extremities and acral sites.

Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) is caused by germline mutations in the FHgene, and is associated with increased incidence of leiomyomas and a potentially aggressive variant of renal cell carcinoma (HLRCC-associated RCC). Absent immunohistochemical expression of fumarate hydratase (FH) has previously been used to diagnose HLRCC-associated RCC, but immunohistochemical staining of leiomyomas is not standard practice. We performed immunohistochemistry (IHC) on whole sections from consecutive cutaneous leiomyomas from our archives to evaluate for both FH and succinate dehydrogenase B expression, in addition to clinicopathologic data collection and review of all hematoxylin and eosin–stained slides for blinded morphologic evaluation of features reported to be seen in HLRCC-associated uterine leiomyomas. Ninety-six cutaneous leiomyomas from 87 patients were identified; 12 of these specimens were from 7 patients with documented HLRCC. FH expression by IHC was absent in 9 specimens and retained in 85 specimens; 2 cases were equivocal with minimal FH expression. Seven of the 9 absent expression specimens were from patients with HLRCC, as were both of the equivocal specimens. The overall sensitivity and specificity of absent FH expression in leiomyomas for detection of patients with HLRCC were 70.0% and 97.6%, respectively. Inclusion of cases classified as equivocal increased sensitivity to 75.0%. Succinate dehydrogenase B expression was retained in 95 specimens and equivocal in 1 specimen. None of the evaluated morphologic features showed any association with leiomyomas in HLRCC. Loss of FH immunohistochemical expression in cutaneous leiomyomas is a sensitive and specific marker for detection of HLRCC, thus suggesting a role for prospective FH IHC in patients with these tumors to screen for HLRCC.

Human papillomavirus (HPV) is an essential causal factor in a subset of head and neck neoplasms, most notably oropharyngeal squamous cell carcinoma, for which HPV infection has important diagnostic, prognostic, and therapeutic implications. This article summarizes the current understanding of HPV-associated neoplasms of the head and neck, including the recently described carcinoma with adenoid cystic-like features. Salient clinical, gross, and microscopic features are discussed, and the utility of specific ancillary studies is highlighted.

IMPORTANCE: Metastasis of cutaneous squamous cell carcinoma (SCC) to the nodal basin is associated with a poor prognosis. The role of sentinel lymph node biopsy (SLNB) for regional staging in patients diagnosed with SCC is unclear. OBJECTIVE: To evaluate a single institution’s experience with use of SLNB for regional staging of SCC on the head and neck. DESIGN, SETTING, AND PARTICIPANTS: A retrospective review of 53 patients who were diagnosed with SCC on the head and neck, at high risk for nodal metastasis based on National Comprehensive Cancer Network (NCCN) risk factors, and treated with wide local excision (WLE) and SLNB from December 1, 2010, through January 30, 2015, in a single academic referral center was performed. The follow-up period ended November 5, 2015. Sentinel lymph node biopsy paraffin blocks were retrieved and processed retrospectively with serial sectioning and immunohistochemical analysis (IHC) in cases with nodal recurrence following a negative SLNB. MAIN OUTCOMES AND MEASURES: Sentinel node (SN) identification rate, SLNB positivity rate, local recurrence, regional nodal recurrence, and distant recurrence. RESULTS: In 53 patients with 54 tumors the SN identification rate was 94%. The SLNB positivity rate was 11.3%. On more thorough tissue processing and IHC, metastatic SCC was identified in 2 of 5 (40%) cases previously deemed negative. After reclassification of these cases, the adjusted SLNB positivity rate was 15.1%. The adjusted rate of false omission was 7.1% (95% CI, 2%-19%). Nodal disease developed in 20.8% overall. Angiolymphatic invasion (Cohen d, 3.52; 95% CI, 1.83-5.21), perineural invasion (Cohen d, 0.81; 95% CI, 0.09-1.52), and clinical size (Cohen d, 0.83; 95% CI, 0.05-1.63) were associated with the presence of nodal disease. CONCLUSIONS AND RELEVANCE: Rigorous study of SLNB for cutaneous SCC incorporating prospectively-collected comprehensive data sets based on standardized treatment algorithms is justified with potential to modify clinical practice. Our study demonstrates the critical importance of serial sectioning and IHC of the SLNB specimen for accurate diagnosis. Use of the NCCN guidelines may facilitate identification of patients with SCC at high risk for nodal metastasis.

Angiosarcoma (AS) is an uncommon vascular malignancy with an aggressive clinical course. Radiation-associated angiosarcoma (RAAS) and Stewart–Treves syndrome are associated with MYC gene amplification and protein overexpression, while other radiation-associated vascular lesions including atypical vascular lesions (AVL) are not associated with MYC overexpression. In contrast, de novoAS represent a group of molecularly heterogeneous tumours, for which MYC expression has not been extensively examined. In this study, MYC immunohistochemistry (IHC) was performed on representative whole tissue sections of a large retrospective cohort of de novoAS, RAAS, Stewart–Treves syndrome, and AVL and evaluated using a semi-quantitative scoring method. MYC is strongly expressed in the majority of RAAS and Stewart–Treves syndrome. De novoAS demonstrate variable MYC expression, with high-grade tumours showing significantly higher MYC expression than low-grade tumours. In contrast, MYC expression in AVL is predominantly negative but may occasionally show focal staining. These results indicate that unequivocal strong MYC IHC staining supports the diagnosis of RAAS. In rare cases of RAAS without strong MYC expression, however, particularly relatively low-grade tumours for which the differential diagnosis includes AVL, the distinction between these lesions should be made on morphological grounds using previously established criteria (i.e., significant atypia, deep invasion, infiltrative growth, etc.). Increased MYC expression in high-grade de novoAS suggests that MYC overexpression may play a role in the pathogenesis of these tumours, and MYC IHC may be a prognostic and/or therapeutic biomarker in a subset of these tumours.

Supplemental Digital Content is available in the text.An emerging group of high-grade renal cell carcinomas (RCCs), particularly carcinomas arising in the hereditary leiomyomatosis renal cell carcinoma syndrome (HLRCC), show fumarate hydratase(FH) gene mutation and loss of function. On the basis of similar cytomorphology and clinicopathologic features between these tumors and cases described as tubulocystic carcinomas with poorly differentiated foci (TC-PD) of infiltrative adenocarcinoma, we hypothesized a relationship between these entities. First, 29 RCCs with morphology of TC-PD were identified retrospectively and assessed for FH expression and aberrant succination (2SC) by immunohistochemistry (IHC), with targeted next-generation sequencing of 409 genes—including FH—performed on a subset. The 29 TC-PD RCCs included 21 males and 8 females, aged 16 to 86 years (median, 46), with tumors measuring 3 to 21 cm (median, 9) arising in the right (n=16) and left (n=13) kidneys. Family history or stigmata of HLRCC were identifiable only retrospectively in 3 (12%). These tumors were aggressive, with 79% showing perinephric extension, nodal involvement in 41%, and metastasis in 86%. Of these, 16 (55%) demonstrated loss of FH by IHC (14/14 with positive 2SC). In contrast, 5 (17%) showed a wild-type immunoprofile of FH+/2SC−. An intriguing group of 8 (28%) showed variable FH± positivity, but with strong/diffuse 2SC+. Next-generation sequencing revealed 8 cases with FHmutations, including 5 FH−/2SC+ and 3 FH±/2SC+ cases, but none in FH+/2SC− cases. Secondly, we retrospectively reviewed the morphology of 2 well-characterized cohorts of RCCs with FH-deficiency determined by IHC or sequencing (n=23 and n=9), unselected for TC-PD pattern, identifying the TC-PD morphology in 10 (31%). We conclude that RCCs with TC-PD morphology are enriched for FH deficiency, and we recommend additional workup, including referral to genetic counseling, for prospective cases. In addition, based on these and other observations, we propose the term “FH-deficient RCC” as a provisional term for tumors with a combination of suggestive morphology and immunophenotype but where genetic confirmation is unavailable upon diagnosis. This term will serve as a provisional nomenclature that will enable triage of individual cases for genetic counseling and testing, while designating these cases for prospective studies of their relationship to HLRCC.

The immunophenotype of a normal testis and the excretory duct system has not been studied comprehensively in fetal and adult patients without testicular disease or hormonal manipulation so far. In addition, testicular (TA) and epididymal (EA) appendages are frequent paratesticular structures without previously reported comprehensive immunophenotypic studies. Immunohistochemistry for multiple markers, including the androgen receptor (AR), the estrogen receptor (ER), the progesterone receptor (PR), the prostate-specific antigen, the prostate-specific membrane antigen, PAX8, WT1, calretinin, CK7, CK20, OCT4, SALL4, and CD117, was performed on full sections of testicular/paratesticular tissue from a large cohort of adult and fetal autopsy patients. In contrast to adult germ cells (GC), fetal GC strongly express OCT4 and CD117, although the expression of these proteins is lost in the early postnatal period; SALL4, in contrast, is expressed in both fetal and adult GC, with only weak and focal expression in adult patients. Fetal Sertoli cells (SC) express WT1 and calretinin strongly and diffusely, in contrast to adult SC. Both fetal and adult excretory duct systems express CK7 and PAX8 with frequent AR coexpression, and all 3 main segments of the excretory duct system (ductuli efferentes, epididymis, and vas deferens) have unique immunophenotypes. The rete testis also has a unique immunohistochemical expression pattern, which includes strong expression of CK7, PAX8, WT1, calretinin, and AR. Finally, of the adult autopsy patients examined, 80% had a TA, and 60% had an EA; these paratesticular structures occurred at stereotypical locations, demonstrated reproducible morphologic features, and had a unique immunophenotype relative to other studied structures, with strong CK7, PAX8, WT1, AR, ER, and PR coexpression. The testis and the paratestis may be involved by diverse neoplastic and non-neoplastic processes, and knowledge of the immunophenotypic expression spectrum of these tissues may aid in clinical diagnosis and advance our understanding of the pathogenesis of both oncologic and nononcologic disease processes.

IMPORTANCE: ERBB2 (formerly HER2) is an important drug target in breast cancer, where anti-ERBB2 therapy has been shown to lead to improvements in disease recurrence and overall survival. ERBB2 status in head and neck squamous cell carcinoma (HNSCC) has not been well studied. Identification of ERBB2-positive tumors and characterization of response to ERBB2 therapy could lead to targeted treatment options in HNSCC. OBJECTIVE: To identify ERBB2 aberrations in HNSCCs and investigate the potential for ERBB2-targeted therapy in HNSCCs. DESIGN, SETTING, AND PARTICIPANTS: A retrospective case series of patients with laryngeal (42 tumor specimens) and oral cavity (94 tumor specimens) SCC enrolled in the University of Michigan Head and Neck Specialized Program of Research Excellence was conducted. Publicly available sequencing data (The Cancer Genome Atlas), as well as data from other studies, were reviewed to identify additional mutations and overexpression in ERBB2 in HNSCC. Established HNSCC cell lines were used for follow-up in vitro analysis. The study was conducted from October 1, 2014, to August 30, 2015. INTERVENTIONS: With the use of targeted, amplicon-based sequencing with the Oncomine Cancer Panel, the copy number and mutation status of commonly altered genes in HNSCCs were assessed. Immunohistochemical staining was performed on tissue microarrays of HNSCCs to assess the expression of ERBB2. Western blotting for HNSCC cell line ERBB2 expression and cell survival assays after treatment with ERBB2 inhibitors were performed. MAIN OUTCOMES AND MEASURES: The prevalence of ERBB2 genetic aberrations and ERBB2 overexpression in laryngeal and oral cavity SCCs, prevalence of ERBB2 aberrations in HNSCC in The Cancer Genome Atlas, ERBB2 protein expression in HNSCC cell lines, and response of HNSCC cell lines to targeted ERBB2 inhibitors. RESULTS: Of the 42 laryngeal SCC samples screened by targeted sequencing, 4 (10%) were positive for ERBB2 amplification. Two of these samples showed ERBB2 overexpression on immunohistochemistry. Two of the 94 oral cavity SCC samples (2%) were positive for ERBB2 on immunohistochemistry. Analysis of 288 patients from publicly available HNSCC sequencing data revealed 9 amplifications (3%) in ERBB2. Protein expression was variable across HNSCC cell lines, and a subset of these cell lines showed responsiveness to anti-ERBB2 therapy. CONCLUSIONS AND RELEVANCE: ERBB2 aberrations were identified in a subset of HNSCCs. These tumors may be responsive to targeted therapy against ERBB2. Screening for ERBB2 aberrations and applying targeted therapy in ERBB2-positive patients may be useful in personalized therapy trials, particularly in patients who are refractory to current treatment paradigms.

IMPORTANCE: Understanding the drainage patterns to the retropharyngeal lymph nodes is an important consideration in oropharyngeal squamous cell carcinoma (OPSCC) because treatment of these nodes is related to increased morbidity. Prediction of these drainage patterns could not only help minimize treatment morbidity but also prevent failures in at-risk patients as deintensification trials are under way for this disease. OBJECTIVE: To evaluate the prevalence of pathologic retropharyngeal adenopathy (RPA) in OPSCC relative to involvement of the oropharyngeal subsite, number of metastatic neck nodes, T classification, and N classification. DESIGN, SETTING, AND PARTICIPANTS: We performed a retrospective review from January 1, 2003, through December 31, 2010, at an academic referral center of 205 previously untreated patients with pathologically confirmed, advanced-stage (III, IV) OPSCC. Data analysis was performed from January 1, 2013, through June 30, 2015. EXPOSURE: Concurrent chemoradiotherapy. MAIN OUTCOMES AND MEASURES: Radiologic evidence of pathologic RPA was tabulated and related to involvement of the oropharyngeal subsite, number of metastatic neck nodes, T classification, and N classification. RESULTS: Of the 205 previously untreated patients (183 men; mean age, 56.1 years), pathologic RPA was identified in 37 (18.0%) of the 205 patients. Pathologic retropharyngeal lymph nodes were found in 12 (13.5%) of 89 patients with base of tongue cancers, 24 (22.0%) of 109 patients with tonsil cancers, and 1 (14.3%) of 7 patients with other oropharyngeal subsite cancers. Increasing prevalence of RPA was positively correlated with closer proximity to the posterior tonsillar pillar. A multivariable logistic regression model using the oropharyngeal subsite, involvement of the posterior tonsillar pillar, number of metastatic neck nodes, T classification, and N classification revealed that the number of metastatic neck nodes was statistically significant (odds ratio, 1.44; 95% CI, 1.20-1.71; P < .001). CONCLUSIONS AND RELEVANCE: The prevalence of pathologic RPA in this cohort was 18.0%, and patients with multiple nodes had the highest risk of pathologic RPA, followed by involvement of the posterior tonsillar pillar. However, these data suggest that there is no clear algorithm that can be used for deintensification to exclude the retropharyngeal site from the treatment volume using extent of disease gathered from pretreatment imaging for patients with advanced-stage OPSCC.

Metanephric adenoma (MA) is a rare benign renal tumor comprised of a neoplastic proliferation of primitive metanephric tubular cells. A previous study identified BRAFV600E mutations in approximately 90 of MA and found that similar BRAFexon 15 mutations are exceedingly rare in other common renal tumors, including renal cell carcinoma and oncocytoma. A recent follow-up study has validated mutation-specific immunohistochemistry (IHC) for detection of BRAFV600E mutations in a small cohort of MA. Here, we extend these findings to a larger, independent cohort of MA, demonstrating an overall 88 sensitivity and 100 specificity for BRAF V600E IHC. In addition, we report 2 cases of MA with novel BRAFexon 15 mutations, including a V600D missense mutation and a compound V600D and K601L missense mutation. Finally, we evaluate BRAF V600E IHC in a large tissue microarray cohort of common renal tumors and find no significant expression in several renal cell carcinoma subtypes. These data support a role for BRAF V600E IHC in diagnostically challenging cases of MA and expand the spectrum of BRAFexon 15 mutations in this uncommon but unique renal neoplasm.

Recent molecular advances have identified a novel, clinically aggressive subgroup of undifferentiated round cell sarcomas defined molecularly by oncogenic fusion of the gene, CIC, and either DUX4 or its paralog, DUX4L, herein termed CIC-DUX sarcomas. Morphologically, CIC-DUX sarcomas are round cell sarcomas with high-grade nuclear features, including vesicular chromatin and nucleoli, patchy clear cell foci, myxoid change, and necrosis. Here, we studied a cohort of 10 cases, including 6 newly identified cases, 2 with paired metastases. Given our prior observation of trisomy 8 in these tumors, we assayed for amplification and expression of MYC (c-Myc) and representative downstream targets. Trisomy 8 was detected in 5/7 testable cases, with further amplification of MYC locus in 6/7 testable cases and immunohistochemical expression of MYC in 10/10. The canonical MYC transcriptional target, p21, but not MTDH, was differentially expressed compared with Ewing sarcomas. Given prior observation of induction of ETS-family transcription factors by the fusion oncoprotein, we assayed and identified highly prevalent positivity for ERG (9/10) and FLI1 (8/8). These findings are cautionary regarding use of these immunostains in prospective case workup, whereas the prevalent MYC amplification may represent a therapeutically targetable oncogenic pathway in CIC-DUX sarcomas.

Classification of small round cell tumors of bone is often challenging due to overlapping clinicopathologic features. The purpose of this article is to review the clinical, radiological, histologic, and molecular features of Ewing sarcoma and to provide a discussion of the differential diagnosis of small round cell tumors of bone.

IMPORTANCE Human papillomaviruses are now recognized as an etiologic factor in a growing subset of head and neck cancers and have critical prognostic importance that affects therapeutic decision making. There is no universally accepted gold standard for high-risk HPV (hrHPV) assessment in formalin-fixed, paraffin-embedded (FFPE) tissue specimens, nor is there a clear understanding of the frequency or role of hrHPV in sites other than oropharynx. OBJECTIVE To determine the optimal assessment of hrHPV in FFPE head and neck tumor tissue specimens. DESIGN, SETTING, PARTICIPANTS In the setting of a large Midwestern referral center, assessment of hrHPV by p16 immunohistochemical staining, in situ hybridization, and polymerase chain reaction (PCR)-MassArray (PCR-MA), with L1 PGMY-PCR and sequencing to resolve method discordance, was conducted for 338 FFPE oropharyngeal, nasopharyngeal, and oral cavity tumor tissue specimens. Relative sensitivity and specificity were compared to develop a standard optimal test protocol. Tissue specimens were collected from 338 patients with head and neck cancer treated during the period 2001 through 2011 in the departments of Otolaryngology, Radiation Oncology, and Medical Oncology. INTERVENTION Patients received standard therapy. MAIN OUTCOMES AND MEASURES Optimal hrHPV identification, detection, and activity in head and neck cancers. RESULTS Using combined PCR-MA with L1 PGMY-PCR and sequencing for conclusive results, we found PCR-MA to have 99.5% sensitivity and 100% specificity, p16 to have 94.2% sensitivity and 85.5% specificity, and in situ hybridization to have 82.9% sensitivity and 81.0% specificity. Among HPV-positive tumors, HPV16 was most frequently detected, but 10 non-HPV16 types accounted for 6% to 50% of tumors, depending on the site. Overall, 86% of oropharynx, 50% of nasopharynx, and 26% of oral cavity tumors were positive for hrHPV. CONCLUSIONS AND RELEVANCE PCR-MA has a low DNA (5 ng) requirement effective for testing small tissue samples; high throughput; and rapid identification of HPV types, with high sensitivity and specificity. PCR-MA together with p16INK4a provided accurate assessment of HPV presence, type, and activity and was determined to be the best approach for HPV testing in FFPE head and neck tumor tissue specimens.

A subset of small round cell sarcomas remains difficult to classify. Among these, a rare tumor harboring a t(4;19)(q35;q13.1) with CIC-DUX4fusion has been described. The aim of this study is to better understand its clinicopathologic features. Four cases of CIC-DUX4sarcoma, all arising in adults (3 women, 1 man, aged 20 to 43 y), were identified using conventional cytogenetic, reverse transcription polymerase chain reaction (RT-PCR) and fluorescence in situ hybridization (FISH) methods. All 4 tumors demonstrated CIC-DUX4fusion transcript by both RT-PCR and FISH and CICrearrangement by FISH. Cytogenetic results from 2 tumors showed t(4;19)(q35;q13.1) occurring as part of a simple karyotype in 1 tumor and as part of a complex karyotype in the other, the latter from a postchemotherapy specimen. Both tumors harbored trisomy 8 and lacked any other known sarcoma-associated translocation. No EWSor SYTrearrangements were detected by RT-PCR or FISH. The tumors had small round cell morphology with a distinctive constellation of histologic features including extensive geographic necrosis, mild nuclear pleomorphism with coarse chromatin and prominent nucleoli, clear cell areas, and focal myxoid matrix. Only focal staining for CD99 was present in each tumor. Two had very focal cytokeratin staining. All tumors were negative for desmin, myogenin, TLE-1, and S100 protein, whereas nuclear INI-1 staining was retained. The tumors were highly aggressive, and all patients died of disseminated disease within 16.8 months. CIC-DUX4sarcoma represents a novel translocation-associated sarcoma with distinctive histopathologic features and rapid disease progression.

Focally enhanced gastritis (FEG) was initially described in patients with inflammatory bowel disease (IBD), but subsequent reports found this to be a nonspecific finding in adults. Initial reports suggest that FEG may be more predictive of IBD in pediatric patients, but this has yet to be confirmed. The aim of our study was to characterize and determine clinical correlates of FEG in pediatric patients. Gastric biopsies from pediatric patients who were diagnosed with FEG at a single tertiary care center over a 5-year period were reviewed (5-y cohort study). In a subsequent study, all gastric biopsies from pediatric patients in the single center over a 1-year period were reviewed. Biopsies were reviewed in a blinded manner by 2 pathologists, and histologic data of interest were recorded. Clinical data and follow-up data were recorded from review of the electronic medical records. Of the 25 patients with FEG in the 5-year cohort study, IBD was present in 19 (76) patients. Crohn disease (CD) was more common than ulcerative colitis (UC) among these patients (68 vs. 16). In the 1-year review study with 262 gastric biopsies, FEG was present in 31 (11) cases. Patients with FEG were significantly more likely to have IBD than non-FEG patients (61.3 vs. 11.6, P0.001). Of the 19 patients with FEG and IBD, 9 patients had CD, 9 patients had UC, and 1 had indeterminate colitis. The presence of FEG is highly associated with IBD in pediatric patients. The presence of FEG does not reliably distinguish between patients with CD and those with UC.

Pleomorphic liposarcoma (PL) is an uncommon form of liposarcoma that rarely occurs in the skin and subcutis. As its behavior in this setting is incompletely characterized, we undertook a study of a series of superficial PLs, defined as those arising or based primarily in the dermis andor subcutis without involvement of deep structures. In addition, MDM2gene amplification, a diagnostic signature of well-differentiateddedifferentiated liposarcoma (WDLDL), was evaluated to address the recent observation that this gene is amplified within PL-like areas in DL. PLs were obtained from institutional and consultation files (n=29). Cases were evaluated with respect to age, sex, location (dermis, dermis and subcutis, subcutis), size, predominant pattern (pleomorphic spindled or epithelioid), extent of lipogenic differentiation, and tumor necrosis. MDM2amplification was analyzed using FISH on formalin-fixed, paraffin-embedded material in 26 cases. Patients ranged in age from 5 to 93 years (M:F=1.4:1). Tumors were located on the extremity (n=15), trunk (n=7), and head and neck (n=7) and involved the dermis (n=4), dermis and subcutis (n=10), and subcutis (n=15). Tumor size ranged from 0.8 to 15 cm (median=2 cm). All were mitotically active high-grade sarcomas FNCLCC grade 2 (n=23) or 3 (n=6) with either a pleomorphic spindled (n=24) or an epithelioid pattern (n=5) with variable extent of lipogenic differentiation <25 (n=15), 25 to 50 (n=9), >50 (n=5). Necrosis was present in 3 cases. MDM2gene amplification was present in 3 of 26 cases. Follow-up information in 24 cases (range=1 to 192 mo; median=48 mo; mean=59 mo) revealed local recurrences (424) but no metastasis or death from disease. We conclude that cutaneous and subcutaneous PLs, despite their high grade, have a much more favorable outcome compared with their deep-seated counterparts, most likely attributed to their small size and superficial location. The low incidence of MDM2gene amplification in our series indicates that most superficial PLs are unrelated to WDLDL. PL likely evolves by way of more than 1 molecular pathway.

Application of Raman spectroscopy to analysis of subchondral bone is described. The effect of cartilage health on subchondral bone has been widely studied using radiological and histological methods; however, there is no method to directly assay mineral components. We present Raman spectra of femur condyles and observe mineral bands that arise from the subchondral bone. In two separate experiments, transgenic mouse models of early-onset osteoarthritis (OA) and lipoatrophy were compared to tissue from wild-type mice. Raman spectroscopy was used to identify chemical changes in the mineral of subchondral bone that may accompany or precede morphological changes that can be observed by histology. The transgenic mice were compared to age-matched wild-type mice. Subtle alterations in the mineral or collagen matrix were observed by Raman spectroscopy using established Raman markers such as the carbonate-to-phosphate ratio, mineral-to-matrix ratio (MTMR), and amide I ratio. The Raman microscope configuration enabled rapid collection of Raman spectra from the mineralized layer that lies under an intact layer of non-mineralized articular cartilage. The effect of the cartilage layer on collection of spectra is discussed. The technique proposed is capable of providing insight into the chemical changes that occur in subchondral bone on a molecular level.

Background: Previous studies have shown that aberrant activation of the Wnt/ß-catenin pathway is associated with many malignant neoplasms. This includes some soft-tissue sarcoma phenotypes, most notably synovial sarcoma, implicating potential targets for novel molecular therapies.Objective: We investigate the level of Wnt/ß-catenin pathway activation present in leiomyosarcomas relative to synovial sarcomas, using expression of LEF1 and ß-catenin as surrogates.Methods: Cancer outlier profile analysis was performed on messenger RNA expression datasets in Oncomine (70 synovial sarcomas, 178 leiomyosarcomas). Results for LEF1 and ß-catenin messenger RNA expression were reported in terms of median-centered intensity. Separate immunohistochemical studies were performed on tissue microarrays created from 77 synovial sarcomas and 89 leiomyosarcomas using antibodies to LEF1 and ß-catenin. Tumors with unequivocal strong nuclear staining involving ?5% of cells were interpreted as positive.Results: Cancer outlier profile analysis demonstrated a higher level of LEF1 messenger RNA expression in synovial sarcomas than in leiomyosarcomas (p?