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Pathogenic variants (mutations) and other molecular events involving subunits of the SWItch/Sucrose Non-Fermentable chromatin remodelling complex are common in a wide variety of malignancies. Many of these neoplasms are characterized by undifferentiated morphology. They arise at a variety of sites in the female genital tract but have rarely been reported in the uterine cervix. We report 2 primary cervical neoplasms arising in young women (ages 28 and 29 yr) exhibiting loss of nuclear immunoreactivity with SMARCB1 (INI1). In one case, which had a mixture of epithelioid and spindle cells, molecular studies revealed no SMARCB1pathogenic variant, but showed a SPECCL1::NTRK 3fusion, in keeping with an NTRK fusion sarcoma. The second case exhibited rhabdoid morphology and molecular testing confirmed a SMARCB1pathogenic variant (c.425 T>G:p.(Leu142Ter) which, interpreted in conjunction with the morphology and immunohistochemistry, resulted in classification as a proximal-type epithelioid sarcoma. To our knowledge, this is the first reported cervical neoplasm exhibiting a SMARCB1pathogenic variant and the first NTRK fusion sarcoma showing SMARCB1 protein loss. We discuss the diagnostic challenges and complexities of the molecular findings.

DICER1 tumor predisposition syndrome results from pathogenic variants in DICER1and is associated with a variety of benign and malignant lesions, typically involving kidney, lung, and female reproductive system. Over 70% of sarcomas in DICER1 tumor predisposition syndrome occur in females. Notably, pediatric cystic nephroma (pCN), a classic DICER1 tumor predisposition syndrome lesion, shows estrogen receptor (ER) expression in stromal cells. There are also renal, hepatic, and pancreatic lesions unassociated with DICER1 tumor predisposition syndrome that have an adult female predominance and are characterized/defined by ER-positive stromal cells. Except for pCN, the expression of ER in DICER1-associated lesions remains uninvestigated. In the present study, ER expression was assessed by immunohistochemistry in 89 cases of DICER1-related lesions and 44 lesions lacking DICER1pathogenic variants. Expression was seen in stromal cells in pCN and pleuropulmonary blastoma (PPB) types I and Ir, whereas anaplastic sarcoma of kidney and PPB types II and III were typically negative, as were other solid tumors of non-Müllerian origin. ER expression was unrelated to the sex or age of the patient. Expression of ER showed an inverse relationship to preferentially expressed antigen in melanoma (PRAME) expression; as lesions progressed from cystic to solid (pCN/anaplastic sarcoma of kidney, and PPB types I to III), ER expression was lost and (PRAME) expression increased. Thus, in DICER1 tumor predisposition syndrome, there is no evidence that non-Müllerian tumors are hormonally driven and antiestrogen therapy is not predicted to be beneficial. Lesions not associated with DICER1pathogenic variants also showed ER-positive stromal cells, including cystic pulmonary airway malformations, cystic renal dysplasia, and simple renal cysts in adult kidneys. ER expression in stromal cells is not a feature of DICER1 perturbation but rather is related to the presence of cystic components.

IMPORTANCE: Magnetic resonance imaging (MRI) surveillance is offered to women with a pathogenic variant in the BRCA1 or BRCA2 gene who face a high lifetime risk of breast cancer. Surveillance with MRI is effective in downstaging breast cancers, but the association of MRI surveillance with mortality risk has not been well defined. OBJECTIVE: To compare breast cancer mortality rates in women with a BRCA1 or BRCA2 sequence variation who entered an MRI surveillance program with those who did not. DESIGN, SETTING, AND PARTICIPANTS: Women with a BRCA1 or BRCA2 sequence variation were identified from 59 participating centers in 11 countries. Participants completed a baseline questionnaire between 1995 and 2015 and a follow-up questionnaire every 2 years to document screening histories, incident cancers, and vital status. Women who had breast cancer, a screening MRI examination, or bilateral mastectomy prior to enrollment were excluded. Participants were followed up from age 30 years (or the date of the baseline questionnaire, whichever was later) until age 75 years, the last follow-up, or death from breast cancer. Data were analyzed from January 1 to July 31, 2023. EXPOSURES: Entrance into an MRI surveillance program. MAIN OUTCOMES AND MEASURES: Cox proportional hazards modeling was used to estimate the hazard ratios (HRs) and 95% CIs for breast cancer mortality associated with MRI surveillance compared with no MRI surveillance using a time-dependent analysis. RESULTS: A total of 2488 women (mean [range] age at study entry 41.2 [30-69] years), with a sequence variation in the BRCA1 (n = 2004) or BRCA2 (n = 484) genes were included in the analysis. Of these participants, 1756 (70.6%) had at least 1 screening MRI examination and 732 women (29.4%) did not. After a mean follow-up of 9.2 years, 344 women (13.8%) developed breast cancer and 35 women (1.4%) died of breast cancer. The age-adjusted HRs for breast cancer mortality associated with entering an MRI surveillance program were 0.20 (95% CI, 0.10-0.43; P < .001) for women with BRCA1 sequence variations and 0.87 (95% CI, 0.10-17.25; P = .93) for women with BRCA2 sequence variations. CONCLUSION AND RELEVANCE: Results of this cohort study suggest that among women with a BRCA1 sequence variation, MRI surveillance was associated with a significant reduction in breast cancer mortality compared with no MRI surveillance. Further studies of women with BRCA2 sequence variations are needed to ascertain these women obtain the same benefits associated with MRI surveillance.

IMPORTANCE: Preventive bilateral salpingo-oophorectomy is offered to women at high risk of ovarian cancer who carry a pathogenic variant in BRCA1 or BRCA2; however, the association of oophorectomy with all-cause mortality has not been clearly defined. OBJECTIVE: To evaluate the association between bilateral oophorectomy and all-cause mortality among women with a BRCA1 or BRCA2 sequence variation. DESIGN, SETTING, AND PARTICIPANTS: In this international, longitudinal cohort study of women with BRCA sequence variations, information on bilateral oophorectomy was obtained via biennial questionnaire. Participants were women with a BRCA1 or BRCA2 sequence variation, no prior history of cancer, and at least 1 follow-up questionnaire completed. Women were followed up from age 35 to 75 years for incident cancers and deaths. Cox proportional hazards regression was used to estimate the hazard ratios (HRs) and 95% CIs for all-cause mortality associated with a bilateral oophorectomy (time dependent). Data analysis was performed from January 1 to June 1, 2023. EXPOSURES: Self-reported bilateral oophorectomy (with or without salpingectomy). MAIN OUTCOMES AND MEASURES: All-cause mortality, breast cancer–specific mortality, and ovarian cancer–specific mortality. RESULTS: There were 4332 women (mean age, 42.6 years) enrolled in the cohort, of whom 2932 (67.8%) chose to undergo a preventive oophorectomy at a mean (range) age of 45.4 (23.0-77.0) years. After a mean follow-up of 9.0 years, 851 women had developed cancer and 228 had died; 57 died of ovarian or fallopian tube cancer, 58 died of breast cancer, 16 died of peritoneal cancer, and 97 died of other causes. The age-adjusted HR for all-cause mortality associated with oophorectomy was 0.32 (95% CI, 0.24-0.42; P < .001). The age-adjusted HR was 0.28 (95% CI, 0.20-0.38; P < .001) and 0.43 (95% CI, 0.22-0.90; P = .03) for women with BRCA1 and BRCA2 sequence variations, respectively. For women with BRCA1 sequence variations, the estimated cumulative all-cause mortality to age 75 years for women who had an oophorectomy at age 35 years was 25%, compared to 62% for women who did not have an oophorectomy. For women with BRCA2 sequence variations, the estimated cumulative all-cause mortality to age 75 years was 14% for women who had an oophorectomy at age 35 years compared to 28% for women who did not have an oophorectomy. CONCLUSIONS AND RELEVANCE: In this cohort study among women with a BRCA1 or BRCA2 sequence variation, oophorectomy was associated with a significant reduction in all-cause mortality.

With the benefit of hindsight, recognition of the cancer susceptibility gene BRCA1and its later cloning were defining moments for breast and ovarian cancer genetics that should be celebrated.

Sertoli-Leydig cell tumors (SLCTs) are uncommon ovarian sex cord-stromal neoplasms which are currently classified into well, moderately, and poorly differentiated and retiform types. Well-differentiated SLCT is the least common and typically occurs in pure form, whereas moderately and poorly differentiated and retiform types often comprise a morphologic spectrum with an admixture of all 3. DICER1pathogenic variants are very common in SLCTs but, as far as we are aware, have not been reported in well-differentiated neoplasms, although the number of cases studied is small due to the rarity of this neoplasm. We undertook DICER1molecular testing in a cohort of 18 well-differentiated SLCTs and show all these to be DICER1wild-type. None of the cases harbored the p.FOXL2C134W hotspot mutation. Based upon the DICER1molecular results, together with morphologic observations, we propose that well-differentiated SLCT is an unrelated neoplasm to the more common moderately/poorly differentiated and retiform SLCTs and is a fundamentally distinct and unrelated tumor type within the ovarian sex cord-stromal tumor family. The implications for tumor nomenclature and recommendations for future tumor classification are discussed within the context of tumors collectively known as SLCTs.

Hereditary cancer syndromes (HCS) predispose individuals to a higher risk of developing multiple cancers. However, current screening strategies have limited ability to screen for all cancer risks. Circulating tumour DNA (ctDNA) detects DNA fragments shed by tumour cells in the bloodstream and can potentially detect cancers early. This study aimed to explore patients’ perspectives on ctDNA’s utility to help inform its clinical adoption and implementation. We conducted a qualitative interpretive description study using semi-structured phone interviews. Participants were purposively sampled adult HCS patients recruited from a Canadian HCS research consortium. Thirty HCS patients were interviewed (n= 19 women, age range 20s-70s, n= 25 were white). Participants were highly concerned about developing cancers, particularly those without reliable screening options for early detection. They “just wanted more” than their current screening strategies. Participants were enthusiastic about ctDNA’s potential to be comprehensive (detect multiple cancers), predictive (detect cancers early) and tailored (lead to personalized clinical management). Participants also acknowledged ctDNA’s potential limitations, including false positives/negatives risks and experiencing additional anxiety. However, they saw ctDNA’s potential benefits outweighing its limitations. In conclusion, participants’ belief in ctDNA’s potential to improve their care overshadowed its limitations, indicating patients’ support for using ctDNA in HCS care.

BackgroundCancer predisposition syndromes (CPSs) are responsible for at least 10% of cancer diagnoses in children and adolescents, most of which are not clinically recognised prior to cancer diagnosis. A variety of clinical screening guidelines are used in healthcare settings to help clinicians detect patients who have a higher likelihood of having a CPS. The McGill Interactive Pediatric OncoGenetic Guidelines (MIPOGG) is an electronic health decision support tool that uses algorithms to help clinicians determine if a child/adolescent diagnosed with cancer should be referred to genetics for a CPS evaluation.MethodsThis study assessed MIPOGG’s performance in identifying Li-Fraumeni, DICER1, Constitutional mismatch repair deficiency and Gorlin (nevoid basal cell carcinoma) syndromes in a retrospective series of 84 children diagnosed with cancer and one of these four CPSs in Canadian hospitals over an 18-year period.ResultsMIPOGG detected 82 of 83 (98.8%) evaluable patients with any one of these four genetic conditions and demonstrated an appropriate rationale for suggesting CPS evaluation. When compared with syndrome-specific clinical screening criteria, MIPOGG’s ability to correctly identify children with any of the four CPSs was equivalent to, or outperformed, existing clinical criteria respective to each CPS.ConclusionThis study adds evidence that MIPOGG is an appropriate tool for CPS screening in clinical practice. MIPOGG’s strength is that it starts with a specific cancer diagnosis and incorporates criteria relevant for associated CPSs, making MIPOGG a more universally accessible diagnostic adjunct that does not require in-depth knowledge of each CPS.

Heterozygous germline pathogenic variants (GPVs) in SMARCA4, the gene encoding the ATP-dependent chromatin remodelling protein SMARCA4 (previously known as BRG1), predispose to several rare tumour types, including small cell carcinoma of the ovary, hypercalcaemic type, atypical teratoid and malignant rhabdoid tumour, and uterine sarcoma. The increase in germline testing of SMARCA4in recent years has revealed putative GPVs affecting SMARCA4in patients with other cancer types. Here we describe 11 patients with neuroblastoma (NBL), including 4 previously unreported cases, all of whom were found to harbour heterozygous germline variants in SMARCA4. Median age at diagnosis was 5 years (range 2 months–26 years); nine were male; and eight of nine cases had tumour location information in the adrenal gland. Eight of the germline variants were expected to result in loss of function of SMARCA4(large deletion, truncating and canonical splice variants), while the remaining four were missense variants. Loss of heterozygosity of the wild-type SMARCA4allele was found in all eight cases where somatic testing was performed, supporting the notion that SMARCA4 functions as a classic tumour suppressor. Altogether, these findings strongly suggest that NBL should be included in the spectrum of SMARCA4-associated tumours.

Signet-ring stromal tumor (SRST) is a rare ovarian stromal neoplasm characterized by a population of bland signet-ring cells, devoid of mucin or lipid, in a generally cellular fibromatous stroma. Previous reports have described heterogenous immunohistochemical and molecular genetic findings, including occasional nuclear β-catenin expression and/or CTNNB1mutations. We report 10 ovarian stromal neoplasms originally diagnosed as SRST. All but 1 tumor underwent detailed immunohistochemical analysis (including β-catenin) and 5 of 10 had CTNNB1mutation analysis performed. All tumors contained a population of morphologically bland signet-ring cells that ranged from 15% to 95% of the neoplasm, characterized by a single large empty intracytoplasmic vacuole, mostly with nuclear indentation. Six of the 10 tumors contained cellular fibroma-like areas, comprising from 10% to 85% of the neoplasm. Three of the 10 tumors were reclassified as microcystic stromal tumor with signet-ring cells on the basis of the microcyst formation and hyalinized stroma, beta-catenin and cyclin D1 nuclear expression and/or CTNNB1mutation, CD10 staining and largely absent expression of inhibin and calretinin. In the remaining 7 tumors, the diagnosis of SRST remained, constituting the largest series of SRST reported in the literature to date. The results of our study suggest that a subset of tumors diagnosed as ovarian SRST, especially those which show β-catenin nuclear positivity and/or CTNNB1mutation, likely represent microcystic stromal tumor with variant morphology. We also suggest that at least a subset of SRSTs without evidence of Wnt/β-catenin pathway abnormalities may be related to ovarian fibromas. We discuss the differential diagnosis of ovarian neoplasms containing signet-ring cells.

A variety of unusual tumors are associated with both germline and somatic DICER1pathogenic variants (PVs), including, in the female genital tract, embryonal rhabdomyosarcoma at various sites and ovarian Sertoli-Leydig cell tumor. There have been occasional reported cases of ovarian germ cell tumors [mainly yolk sac tumor (YST)] harboring DICER1PVs but, as far as we are aware, none of these has been proven to have a germline provenance. We report an unusual enteric variant of ovarian YST in a 28-yr-old woman associated with a germline PV c.901C>T (p.Gln301Ter) in exon 7 of DICER1, accompanied by a somatic (YST-only) hotspot mutation: c.5437G>A, p.E1813K. To our knowledge, this is the first report of an ovarian germ cell tumor associated with a germline DICER1PV. We review other reported cases of ovarian germ cell tumor with DICER1PVs and discuss the differential diagnosis of this unusual variant of YST which was originally diagnosed as a mucinous adenocarcinoma.

Small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) is an extremely rare, highly aggressive cancer (mean age of onset, 24 years). Nearly all cases are associated with somatic or germline pathogenic variants (GPVs) in SMARCA4. Early bilateral oophorectomy is recommended for unaffected females with a SMARCA4GPV. However, the penetrance of SMARCA4GPVs for SCCOHT is highly uncertain and subject to ascertainment bias.

BackgroundConstitutional mismatch repair deficiency syndrome (CMMRD) is the most aggressive cancer predisposition syndrome associated with multiorgan cancers, often presenting in childhood. There is variability in age and presentation of cancers and benign manifestations mimicking neurofibromatosis type 1. Genetic testing may not be informative and is complicated by pseudogenes associated with the most commonly associated gene, PMS2. To date, no diagnostic criteria exist. Since surveillance and immune-based therapies are available, establishing a CMMRD diagnosis is key to improve survival.MethodsIn order to establish a robust diagnostic path, a multidisciplinary international working group, with representation from the two largest consortia (International Replication Repair Deficiency (IRRD) consortium and European Consortium Care for CMMRD (C4CMMRD)), was formed to establish diagnostic criteria based on expertise, literature review and consensus.ResultsThe working group established seven diagnostic criteria for the diagnosis of CMMRD, including four definitive criteria (strong evidence) and three likely diagnostic criteria (moderate evidence). All criteria warrant CMMRD surveillance. The criteria incorporate germline mismatch repair results, ancillary tests and clinical manifestation to determine a diagnosis. Hallmark cancers for CMMRD were defined by the working group after extensive literature review and consultation with the IRRD and C4CMMRD consortia.ConclusionsThis position paper summarises the evidence and rationale to provide specific guidelines for CMMRD diagnosis, which necessitates appropriate surveillance and treatment.

BackgroundGermline pathogenic variants in DICER1cause DICER1 syndrome, an autosomal dominant, pleiotropic tumour predisposition syndrome with variable expressivity and reduced penetrance for specific dysplastic and neoplastic lesions. Recently, a syndrome with the acronym GLOW (Global developmental delay, Lung cysts, Overgrowth, Wilms tumour) was described in two children with mosaic missense mutations in hotspot residues of the DICER1 RNase IIIb domain.MethodsWhole genome sequencing, exome sequencing, Sanger sequencing, digital PCR and a review of Wilms tumours with DICER1RNase III domain mutations were performed.ResultsA de novo heterozygous c.4031C>T (p.S1344L) variant in the sequence encoding the RNase IIIa domain of DICER1was detected. Clinical investigations revealed a phenotype that resembles the GLOW subphenotype of DICER1 syndrome.ConclusionThe phenotypic overlap between patients with p.S1344L mutation and GLOW syndrome provide clinical support for recent discoveries that RNase IIIa-Ser1344 site mutations impede miRNA-5p biogenesis analogous to DICER1hotspot mutations in the RNase IIIb domain. We show that an individual with a heterozygous germline p.S1344L mutation has a severe form of DICER1 syndrome (‘DICER1 syndrome plus’), with notable features of intellectual disability, macrocephaly, physical abnormalities, Wilms tumour and a well-differentiated fetal adenocarcinoma of the lung.

BackgroundThis study aimed to identify and resolve discordant variant interpretations across clinical molecular genetic laboratories through the Canadian Open Genetics Repository (COGR), an online collaborative effort for variant sharing and interpretation.MethodsLaboratories uploaded variant data to the Franklin Genoox platform. Reports were issued to each laboratory, summarising variants where conflicting classifications with another laboratory were noted. Laboratories could then reassess variants to resolve discordances. Discordance was calculated using a five-tier model (pathogenic (P), likely pathogenic (LP), variant of uncertain significance (VUS), likely benign (LB), benign (B)), a three-tier model (LP/P are positive, VUS are inconclusive, LB/B are negative) and a two-tier model (LP/P are clinically actionable, VUS/LB/B are not). We compared the COGR classifications to automated classifications generated by Franklin.ResultsTwelve laboratories submitted classifications for 44 510 unique variants. 2419 variants (5.4%) were classified by two or more laboratories. From baseline to after reassessment, the number of discordant variants decreased from 833 (34.4% of variants reported by two or more laboratories) to 723 (29.9%) based on the five-tier model, 403 (16.7%) to 279 (11.5%) based on the three-tier model and 77 (3.2%) to 37 (1.5%) based on the two-tier model. Compared with the COGR classification, the automated Franklin classifications had 94.5% sensitivity and 96.6% specificity for identifying actionable (P or LP) variants.ConclusionsThe COGR provides a standardised mechanism for laboratories to identify discordant variant interpretations and reduce discordance in genetic test result delivery. Such quality assurance programmes are important as genetic testing is implemented more widely in clinical care.

BackgroundTraditional medical genetics models are unable to meet the growing demand for germline genetic testing (GT) in patients with exocrine pancreatic cancer (PC). This study investigates the impact of an ambulatory oncology clinic-based GT model.MethodsFrom 2012 to 2021, patients with PC were prospectively enrolled and considered for GT. Two chronological cohorts were compared: (1) the preuniversal genetic testing (pre-UGT) cohort, which received GT based on clinical criteria or family history; and (2) the post-UGT cohort, where an 86-gene panel was offered to all patients with PC.ResultsOf 847 eligible patients, 735 (86.8%) were enrolled (pre-UGT, n=579; post-UGT, n=156). A higher proportion of the post-UGT cohort received prospective GT (97.4% vs 58.5%, p<0.001). The rate of pathogenic germline alterations (PGA) across both cohorts was 9.9%, with 8.0% of PGAs in PC susceptibility genes. The post-UGT cohort had a higher prevalence of overall PGAs (17.2% vs 6.6%, p<0.001) and PGAs in PC susceptibility genes (11.9% vs 6.3%, p<0.001). The median turnaround time from enrolment to GT report was shorter in the post-UGT cohort (13 days vs 42 days, p<0.001). Probands with a PGA disclosed their GT results to 84% of their first-degree relatives (FDRs). However, only 31% of informed FDRs underwent GT, and the number of new cases per index case was 0.52.ConclusionA point-of-care GT model is feasible and expedites access to GT for patients with PC. Strategies to increase the uptake of cascade testing are needed to maximise the clinical impact of an oncology clinic-based GT model.

IMPORTANCE: Prompt recognition of a child with a cancer predisposition syndrome (CPS) has implications for cancer management, surveillance, genetic counseling, and cascade testing of relatives. Diagnosis of CPS requires practitioner expertise, access to genetic testing, and test result interpretation. This diagnostic process is not accessible in all institutions worldwide, leading to missed CPS diagnoses. Advances in electronic health technology can facilitate CPS risk assessment. OBJECTIVE: To evaluate the diagnostic accuracy of a CPS prediction tool (McGill Interactive Pediatric OncoGenetic Guidelines [MIPOGG]) in identifying children with cancer who have a low or high likelihood of having a CPS. DESIGN, SETTING, AND PARTICIPANTS: In this international, multicenter diagnostic accuracy study, 1071 pediatric (&lt;19 years of age) oncology patients who had a confirmed CPS (12 oncology referral centers) or who underwent germline DNA sequencing through precision medicine programs (6 centers) from January 1, 2000, to July 31, 2020, were studied. EXPOSURES: Exposures were MIPOGG application in patients with cancer and a confirmed CPS (diagnosed through routine clinical care; n = 413) in phase 1 and MIPOGG application in patients with cancer who underwent germline DNA sequencing (n = 658) in phase 2. Study phases did not overlap. Data analysts were blinded to genetic test results. MAIN OUTCOMES AND MEASURES: The performance of MIPOGG in CPS recognition was compared with that of routine clinical care, including identifying a CPS earlier than practitioners. The tool’s test characteristics were calculated using next-generation germline DNA sequencing as the comparator. RESULTS: In phase 1, a total of 413 patients with cancer (median age, 3.0 years; range, 0-18 years) and a confirmed CPS were identified. MIPOGG correctly recognized 410 of 412 patients (99.5%) as requiring referral for CPS evaluation at the time of primary cancer diagnosis. Nine patients diagnosed with a CPS by a practitioner after their second malignant tumor were detected by MIPOGG using information available at the time of the first cancer. In phase 2, of 658 children with cancer (median age, 6.6 years; range, 0-18.8 years) who underwent comprehensive germline DNA sequencing, 636 had sufficient information for MIPOGG application. When compared with germline DNA sequencing for CPS detection, the MIPOGG test characteristics for pediatric-onset CPSs were as follows: sensitivity, 90.7%; specificity, 60.5%; positive predictive value, 17.6%; and negative predictive value, 98.6%. Tumor DNA sequencing data confirmed the MIPOGG recommendation for CPS evaluation in 20 of 22 patients with established cancer-CPS associations. CONCLUSIONS AND RELEVANCE: In this diagnostic study, MIPOGG exhibited a favorable accuracy profile for CPS screening and reduced time to CPS recognition. These findings suggest that MIPOGG implementation could standardize and rationalize recommendations for CPS evaluation in children with cancer.

Herein we evaluated a series of 21 embryonal rhabdomyosarcomas of the uterine corpus (ucERMS), a rare neoplasm, to characterize their morphology, genomics, and behavior. Patients ranged from 27 to 73 (median 52) years and tumors from 4 to 15 (median 9) cm, with extrauterine disease noted in two. Follow-up (median 16 months) was available for 14/21 patients; nine were alive and well, four died of disease, and one died from other causes. Most tumors (16/21) showed predominantly classic morphology, comprised of alternating hyper- and hypocellular areas of primitive small cells and differentiating rhabdomyoblasts in a loose myxoid/edematous stroma. A cambium layer was noted in all; seven had heterologous elements (six with fetal-type cartilage) and eight displayed focal anaplasia. The remaining five neoplasms showed only a minor component (≤20%) of classic morphology, with anaplasia noted in four and tumor cell necrosis in three. The most frequent mutations detected were in DICER1(14/21), TP53(7/20), PI3K/AKT/mTOR pathway (7/20), and KRAS/NRAS(5/20). Copy-number alterations were present in 10/19 tumors. Overall, 8/14 DICER1-associated ucERMS showed concurrent loss of function and hotspot mutations in DICER1, which is a feature more likely to be seen in tumors associated with DICER1 syndrome. Germline data were available for two patients, both DICER1wild type (one with concurrent loss of function and hotspot alterations). DICER1-associated ucERMS were more likely to show a classic histological appearance including heterologous elements than DICER1-independent tumors. No differences in survival were noted between the two groups, but both patients with extrauterine disease at diagnosis and two with recurrences died from disease. As no patients had a known personal or family history of DICER1 syndrome, we favor most DICER1-associated ucERMS to be sporadic.

Herein we evaluated a series of 21 embryonal rhabdomyosarcomas of the uterine corpus (ucERMS), a rare neoplasm, to characterize their morphology, genomics, and behavior. Patients ranged from 27 to 73 (median 52) years and tumors from 4 to 15 (median 9) cm, with extrauterine disease noted in two. Follow-up (median 16 months) was available for 14/21 patients; nine were alive and well, four died of disease, and one died from other causes. Most tumors (16/21) showed predominantly classic morphology, comprised of alternating hyper- and hypocellular areas of primitive small cells and differentiating rhabdomyoblasts in a loose myxoid/edematous stroma. A cambium layer was noted in all; seven had heterologous elements (six with fetal-type cartilage) and eight displayed focal anaplasia. The remaining five neoplasms showed only a minor component (≤20%) of classic morphology, with anaplasia noted in four and tumor cell necrosis in three. The most frequent mutations detected were in DICER1(14/21), TP53(7/20), PI3K/AKT/mTOR pathway (7/20), and KRAS/NRAS(5/20). Copy-number alterations were present in 10/19 tumors. Overall, 8/14 DICER1-associated ucERMS showed concurrent loss of function and hotspot mutations in DICER1, which is a feature more likely to be seen in tumors associated with DICER1 syndrome. Germline data were available for two patients, both DICER1wild type (one with concurrent loss of function and hotspot alterations). DICER1-associated ucERMS were more likely to show a classic histological appearance including heterologous elements than DICER1-independent tumors. No differences in survival were noted between the two groups, but both patients with extrauterine disease at diagnosis and two with recurrences died from disease. As no patients had a known personal or family history of DICER1 syndrome, we favor most DICER1-associated ucERMS to be sporadic.

PALB2germline pathogenic variants are associated with increased breast cancer risk and smaller increased risk of pancreatic and likely ovarian cancer. Resources for health-care professionals managing PALB2heterozygotes are currently limited.

Introduction:With the use of ultrasonography for the evaluation of thyroid and nonthyroid neck diseases, the incidental discovery of previously unsuspected thyroid nodules/nonpalpable lesions has increased. Intrathyroidal thymus arises due to aberrant thymic migration during embryogenesis. It is thought to be rare, fulfils the classiccriteria for diagnosis of an incidentaloma and it can be mistaken for a thyroid nodule. Multinodular goiter is the main endocrine manifestation of DICER1 syndrome, a tumor predisposition syndrome. Careful thyroid examination including ultrasound is thus necessary for DICER1 syndrome patients. Case Report:A 4-year-old prepubertal boy was referred to the pediatric endocrinology department following an earlier diagnosis of pleuropulmonary blastoma (PPB) type III, which is a hallmark component of DICER1 syndrome. The patient underwent surgery followed by chemotherapy. Genetic analysis identified a germline DICER1pathogenic variant (c.2062C>T, p.R688*)in the child and in 5 relatives. A second somatic DICER1RNase IIIb hotspot mutation(c.5438A>G, p.E1813G) was identified in DNA extracted from the proband’s PPB. He had no goiter on clinical examination, but a heterogenous, well-delineated, avascular, solid and hypoechogenic lesion with pseudomicrocalcifications was observed in the right lobe (4.1 × 3.1 × 2.6 mm), suggestive of thyroid neoplasia. Diagnostic work-up and a 3-year follow-up excluded thyroid neoplasia and confirmed the diagnosis of an intrathyroid benign thymic lesion. Discussion and Conclusion:This case exemplifies that thyroid incidentalomas in DICER1 syndrome patients should be viewed with great suspicion, but that not all thyroid disorders are indeed DICER1-related in these patients.

Introduction:With the use of ultrasonography for the evaluation of thyroid and nonthyroid neck diseases, the incidental discovery of previously unsuspected thyroid nodules/nonpalpable lesions has increased. Intrathyroidal thymus arises due to aberrant thymic migration during embryogenesis. It is thought to be rare, fulfils the classiccriteria for diagnosis of an incidentaloma and it can be mistaken for a thyroid nodule. Multinodular goiter is the main endocrine manifestation of DICER1 syndrome, a tumor predisposition syndrome. Careful thyroid examination including ultrasound is thus necessary for DICER1 syndrome patients. Case Report:A 4-year-old prepubertal boy was referred to the pediatric endocrinology department following an earlier diagnosis of pleuropulmonary blastoma (PPB) type III, which is a hallmark component of DICER1 syndrome. The patient underwent surgery followed by chemotherapy. Genetic analysis identified a germline DICER1pathogenic variant (c.2062C>T, p.R688*)in the child and in 5 relatives. A second somatic DICER1RNase IIIb hotspot mutation(c.5438A>G, p.E1813G) was identified in DNA extracted from the proband’s PPB. He had no goiter on clinical examination, but a heterogenous, well-delineated, avascular, solid and hypoechogenic lesion with pseudomicrocalcifications was observed in the right lobe (4.1 × 3.1 × 2.6 mm), suggestive of thyroid neoplasia. Diagnostic work-up and a 3-year follow-up excluded thyroid neoplasia and confirmed the diagnosis of an intrathyroid benign thymic lesion. Discussion and Conclusion:This case exemplifies that thyroid incidentalomas in DICER1 syndrome patients should be viewed with great suspicion, but that not all thyroid disorders are indeed DICER1-related in these patients.

The spectrum of neoplasms associated with DICER1variants continues to expand, with the recent addition of primary “DICER1-associated central nervous system sarcoma” (DCS). DCS is a high-grade malignancy predominantly affecting pediatric patients. Six pediatric DCS were identified through a combination of clinical diagnostic studies, archival inquiry, and interinstitutional collaboration. Clinical, histologic, immunohistologic, and molecular features were examined. Genomic findings in the 6 DCS were compared with those in 14 additional DICER1-associated tumors sequenced with the same assay. The six patients presented at ages 3–15 years with CNS tumors located in the temporal (n= 2), parietal (n= 1), fronto-parietal (n= 1), and frontal (n= 2) lobes. All underwent surgical resection. Histologic examination demonstrated high-grade malignant spindle cell tumors with pleuropulmonary blastoma-like embryonic “organoid” features and focal rhabdomyoblastic differentiation; immature cartilage was seen in one case. Immunohistochemically, there was patchy desmin and myogenin staining, and patchy loss of H3K27me3, and within eosinophilic cytoplasmic globules, alfa-fetoprotein staining. Biallelic DICER1variants were identified in all cases, with germline variants in two of five patients tested. DCS demonstrated genomic alterations enriched for Ras pathway activation and TP53inactivation. Tumor mutational burden was significantly higher in the 6 DCS tumors than in 14 other DICER1-associated tumors examined (mean 12.9 vs. 6.8 mutations/Mb, p= 0.035). Postoperative care included radiation (n= 5) and chemotherapy (n= 3); at the last follow-up, three patients were alive without DCS, and three had died of disease. Our analysis expands the clinical, histologic, immunohistological, and molecular spectrum of DCS, identifying distinctive features that can aid in the diagnosis, multidisciplinary evaluation, and treatment of DCS.

Molecular profiling was performed in 50 problematic ovarian sex cord-stromal tumours (SCSTs) most of which were seen in consultation. Following analysis, 17 were classified as adult granulosa cell tumour (AGCT), 16 of which showed a FOXL2sequence variant (mutation); the initial favoured diagnosis in five of the cases was benign thecoma/fibrothecoma. Thirteen tumours ultimately classified as cellular fibroma or thecoma were FOXL2sequence variant negative which was helpful in excluding AGCT. All six Sertoli–Leydig cell tumours (SLCTs) demonstrated DICER1‘hot spot’ sequence variants, and one case each of AGCT and SLCT showed high grade histological transformation associated with a concurrent TP53sequence variant. All eight unclassified SCSTs were negative for FOXL2mutations and the six tested cases were DICER1wild type; however, three tumours demonstrated MET, CTNNB1or TP53sequence variants. Four cases were classified as juvenile granulosa cell tumour, and one of these harboured a GNASsequence variant. The single gynandroblastoma and microcystic stromal tumours in the series demonstrated FOXL2and CTNNB1alterations, respectively. In summary, molecular analysis aids in accurate classification of challenging ovarian SCSTs and sometimes leads to revision of the favoured provisional diagnosis. TP53sequence variants may be associated with dedifferentiation in both SLCTs and AGCTs.

The spectrum of neoplasms associated with DICER1variants continues to expand, with the recent addition of primary “DICER1-associated central nervous system sarcoma” (DCS). DCS is a high-grade malignancy predominantly affecting pediatric patients. Six pediatric DCS were identified through a combination of clinical diagnostic studies, archival inquiry, and interinstitutional collaboration. Clinical, histologic, immunohistologic, and molecular features were examined. Genomic findings in the 6 DCS were compared with those in 14 additional DICER1-associated tumors sequenced with the same assay. The six patients presented at ages 3–15 years with CNS tumors located in the temporal (n= 2), parietal (n= 1), fronto-parietal (n= 1), and frontal (n= 2) lobes. All underwent surgical resection. Histologic examination demonstrated high-grade malignant spindle cell tumors with pleuropulmonary blastoma-like embryonic “organoid” features and focal rhabdomyoblastic differentiation; immature cartilage was seen in one case. Immunohistochemically, there was patchy desmin and myogenin staining, and patchy loss of H3K27me3, and within eosinophilic cytoplasmic globules, alfa-fetoprotein staining. Biallelic DICER1variants were identified in all cases, with germline variants in two of five patients tested. DCS demonstrated genomic alterations enriched for Ras pathway activation and TP53inactivation. Tumor mutational burden was significantly higher in the 6 DCS tumors than in 14 other DICER1-associated tumors examined (mean 12.9 vs. 6.8 mutations/Mb, p= 0.035). Postoperative care included radiation (n= 5) and chemotherapy (n= 3); at the last follow-up, three patients were alive without DCS, and three had died of disease. Our analysis expands the clinical, histologic, immunohistological, and molecular spectrum of DCS, identifying distinctive features that can aid in the diagnosis, multidisciplinary evaluation, and treatment of DCS.

Cell division and organismal development are exquisitely orchestrated and regulated processes. The dysregulation of the molecular mechanisms underlying these processes may cause cancer, a consequence of cell-intrinsic and/or cell-extrinsic events. Cellular DNA can be damaged by spontaneous hydrolysis, reactive oxygen species, aberrant cellular metabolism or other perturbations that cause DNA damage. Moreover, several environmental factors may damage the DNA, alter cellular metabolism or affect the ability of cells to interact with their microenvironment. While some environmental factors are well established as carcinogens, there remains a large knowledge gap of others owing to the difficulty in identifying them because of the typically long interval between carcinogen exposure and cancer diagnosis. DNA damage increases in cells harbouring mutations that impair their ability to correctly repair the DNA. Tumour predisposition syndromes in which cancers arise at an accelerated rate and in different organs — the equivalent of a sensitized background — provide a unique opportunity to examine how gene–environment interactions influence cancer risk when the initiating genetic defect responsible for malignancy is known. Understanding the molecular processes that are altered by specific germline mutations, environmental exposures and related mechanisms that promote cancer will allow the design of novel and effective preventive and therapeutic strategies.

Poorly differentiated thyroid carcinomas (PDTC) in young individuals are rare and their clinical and histopathologic features, genetic mechanisms, and outcomes remain largely unknown. Here, we report a detailed characterization of a series of six PDTC in patients ≤21 years old defined by Turin diagnostic criteria studied for mutations and gene fusions characteristic of thyroid cancer using targeted next-generation sequencing (NGS) and whole-exome sequencing (WES). All tumors had solid, insular, or trabecular growth pattern and high mitotic rate, and five out of six tumors showed tumor necrosis. Targeted NGS assay identified somatic mutations in the DICER1gene in five of six (83%) tumors, all of which were “hotspot” mutations encoding the metal-ion binding sites of the RNase IIIb domain of DICER1. WES was performed in five cases which confirmed all hotspot mutations and detected two tumors with additional inactivating DICER1alterations. Of these two, one was a germline pathogenic DICER1variant and the other had loss of heterozygosity for DICER1. No other mutations or gene fusions characteristic of adult well-differentiated thyroid cancer and PDTC (BRAF, RAS, TERT, RET/PTC,and other) were detected. On follow-up, available for five patients, three patients died of disease 8–24 months after diagnosis, whereas two were alive with no disease. The results of our study demonstrate that childhood- and adolescent-onset PDTC are genetically distinct from adult-onset PDTC in that they are strongly associated with DICER1mutations and may herald DICER1 syndrome in a minority. As such, all young persons with PDTC may benefit from genetic counseling. Furthermore, their clinically aggressive behavior contrasts sharply with the indolent nature of the great majority of thyroid tumors with DICER1mutations reported to date.

Poorly differentiated thyroid carcinomas (PDTC) in young individuals are rare and their clinical and histopathologic features, genetic mechanisms, and outcomes remain largely unknown. Here, we report a detailed characterization of a series of six PDTC in patients ≤21 years old defined by Turin diagnostic criteria studied for mutations and gene fusions characteristic of thyroid cancer using targeted next-generation sequencing (NGS) and whole-exome sequencing (WES). All tumors had solid, insular, or trabecular growth pattern and high mitotic rate, and five out of six tumors showed tumor necrosis. Targeted NGS assay identified somatic mutations in the DICER1gene in five of six (83%) tumors, all of which were “hotspot” mutations encoding the metal-ion binding sites of the RNase IIIb domain of DICER1. WES was performed in five cases which confirmed all hotspot mutations and detected two tumors with additional inactivating DICER1alterations. Of these two, one was a germline pathogenic DICER1variant and the other had loss of heterozygosity for DICER1. No other mutations or gene fusions characteristic of adult well-differentiated thyroid cancer and PDTC (BRAF, RAS, TERT, RET/PTC,and other) were detected. On follow-up, available for five patients, three patients died of disease 8–24 months after diagnosis, whereas two were alive with no disease. The results of our study demonstrate that childhood- and adolescent-onset PDTC are genetically distinct from adult-onset PDTC in that they are strongly associated with DICER1mutations and may herald DICER1 syndrome in a minority. As such, all young persons with PDTC may benefit from genetic counseling. Furthermore, their clinically aggressive behavior contrasts sharply with the indolent nature of the great majority of thyroid tumors with DICER1mutations reported to date.

DICER1mutations (somatic or germline) are associated with a variety of uncommon neoplasms including cervical and genitourinary embryonal rhabdomyosarcoma (ERMS). We report a primary ovarian and 2 primary fallopian tube ERMS occurring in 60-, 13-, and 14-year-olds, respectively. The 3 neoplasms exhibited a similar morphologic appearance being polypoid and containing edematous hypocellular areas and hypercellular foci composed of small cells with scant cytoplasm exhibiting rhabdomyoblastic differentiation (desmin, myogenin, myoD1 positive). There was cellular cartilage in all cases and extensive foci of anaplasia, eosinophilic globules, and bone/osteoid in 1 case each. All 3 neoplasms exhibited DICER1mutations; in 1 of the tubal cases, the patient had a germline mutation and in the other 2 cases, the DICER1mutations were somatic. Accompanying DICER1“second hits” were identified in all cases. In 2 of the neoplasms, SALL4-positive glandular structures were present which we speculate may represent an unusual primitive “metaplastic” phenomenon. Our study adds to the literature on ERMS at unusual sites associated with DICER1mutations. ERMS arising at such sites, especially when they contain cartilage or bone/osteoid, are especially likely to be associated with DICER1mutations. Pathologists should be aware of this as these may be the sentinel neoplasms in patients with DICER1syndrome and confirming a germline mutation can facilitate the screening of the individual and affected family members for other neoplasms which occur in this syndrome.

Embryonal rhabdomyosarcomas (ERMS) account for 2–3% of cancers in pediatric and adolescent populations. They are rarer in adults. We and others have reported that ERMS arising in the uterine cervix may harbor mutations in the gene encoding the microRNA biogenesis enzyme, DICER1, but a large series of cases has not been published. In the uterus, distinguishing ERMS from adenosarcoma can be very challenging, even for expert pathologists, and DICER1alterations have been identified in a variable subset of uterine adenosarcomas. We hypothesized that DICER1genetic testing may be useful in distinguishing between ERMS and adenosarcoma. We conducted a central pathology review-based study of 64 tumors initially thought to be uterine ERMS or adenosarcoma; 19 neoplasms had a consensus diagnosis of ERMS, 27 of adenosarcoma and for 18, no consensus diagnosis was reached. The median age at diagnosis was 30 years (range 2.5–69) for ERMS, 57.5 years (range 27–82) for adenosarcoma, and 65.5 years (range 32–86) for no consensus cases. In our series, the DICER1mutation prevalence differed between the three groups: DICER1alterations were present in 18/19 (95%) ERMS, 7/27 (26%) adenosarcomas (p< 0.001), and 4/18 (22%) no consensus cases. A germline alteration was present in 6/12 ERMS patients tested versus 0/6 adenosarcoma patients. Thus, although DICER1mutations are near ubiquitous in uterine ERMS and are significantly less common in uterine adenosarcoma, DICER1testing is only of value in distinguishing between the two neoplasms when a DICER1mutation is absent, as this is helpful in excluding ERMS. On review of the clinical and radiological features of the single DICER1wild-type cervical ERMS, this was thought most likely to be of vaginal origin. Given the significant prevalence of DICER1germline pathogenic variants in uterine ERMS, all patients with this diagnosis should be referred to a genetics service.

Embryonal rhabdomyosarcomas (ERMS) account for 2–3% of cancers in pediatric and adolescent populations. They are rarer in adults. We and others have reported that ERMS arising in the uterine cervix may harbor mutations in the gene encoding the microRNA biogenesis enzyme, DICER1, but a large series of cases has not been published. In the uterus, distinguishing ERMS from adenosarcoma can be very challenging, even for expert pathologists, and DICER1alterations have been identified in a variable subset of uterine adenosarcomas. We hypothesized that DICER1genetic testing may be useful in distinguishing between ERMS and adenosarcoma. We conducted a central pathology review-based study of 64 tumors initially thought to be uterine ERMS or adenosarcoma; 19 neoplasms had a consensus diagnosis of ERMS, 27 of adenosarcoma and for 18, no consensus diagnosis was reached. The median age at diagnosis was 30 years (range 2.5–69) for ERMS, 57.5 years (range 27–82) for adenosarcoma, and 65.5 years (range 32–86) for no consensus cases. In our series, the DICER1mutation prevalence differed between the three groups: DICER1alterations were present in 18/19 (95%) ERMS, 7/27 (26%) adenosarcomas (p< 0.001), and 4/18 (22%) no consensus cases. A germline alteration was present in 6/12 ERMS patients tested versus 0/6 adenosarcoma patients. Thus, although DICER1mutations are near ubiquitous in uterine ERMS and are significantly less common in uterine adenosarcoma, DICER1testing is only of value in distinguishing between the two neoplasms when a DICER1mutation is absent, as this is helpful in excluding ERMS. On review of the clinical and radiological features of the single DICER1wild-type cervical ERMS, this was thought most likely to be of vaginal origin. Given the significant prevalence of DICER1germline pathogenic variants in uterine ERMS, all patients with this diagnosis should be referred to a genetics service.

Genome-wide association studies have identified breast cancer risk variants in over 150 genomic regions, but the mechanisms underlying risk remain largely unknown. These regions were explored by combining association analysis with in silico genomic feature annotations. We defined 205 independent risk-associated signals with the set of credible causal variants in each one. In parallel, we used a Bayesian approach (PAINTOR) that combines genetic association, linkage disequilibrium and enriched genomic features to determine variants with high posterior probabilities of being causal. Potentially causal variants were significantly over-represented in active gene regulatory regions and transcription factor binding sites. We applied our INQUSIT pipeline for prioritizing genes as targets of those potentially causal variants, using gene expression (expression quantitative trait loci), chromatin interaction and functional annotations. Known cancer drivers, transcription factors and genes in the developmental, apoptosis, immune system and DNA integrity checkpoint gene ontology pathways were over-represented among the highest-confidence target genes.

Embryonal rhabdomyosarcoma of the uterine cervix is a rare neoplasm which is almost invariably associated with pathogenic somatic or germline DICER1mutations; patients with germline mutations have DICER1 syndrome. We report 2 subtle cervical embryonal rhabdomyosarcoma, one occurring in a 21-yr-old woman with a known history of DICER1 syndrome and the other in a 19-yr-old woman with no history of DICER1 syndrome or DICER1-associated neoplasms. Both neoplasms focally involved otherwise benign endocervical polyps and were characterized histologically by subtle areas of increased stromal cellularity, nuclear atypia and mitotic activity; there was focal nuclear staining of these areas with the skeletal muscle markers myogenin and myoD1. In both cases, demonstration of a somatic DICER1RNase IIIb mutation in the tumor was instrumental in establishing the diagnosis. We believe these neoplasms represent the earliest discernible phase of cervical embryonal rhabdomyosarcoma. Pathologists should have a high index of suspicion when atypical stromal elements are present in endocervical polyps and immunohistochemistry together with DICER1sequencing will assist in diagnosis.

Dedifferentiated and undifferentiated ovarian carcinomas (DDOC/UDOC) are rare neoplasms defined by the presence of an undifferentiated carcinoma. In this study, we detailed the clinical, pathological, immunohistochemical, and molecular features of a series of DDOC/UDOC. We collected a multi-institutional cohort of 23 DDOC/UDOC and performed immunohistochemistry for core switch/sucrose nonfermentable (SWI/SNF) complex proteins (ARID1A, ARID1B, SMARCA4, and SMARCB1), mismatch repair (MMR) proteins, and p53. Array-based genome-wide DNA methylation and copy number variation analyses were performed on a subset of cases with comparison made to a previously reported cohort of undifferentiated endometrial carcinoma (UDEC), small cell carcinoma of the ovary, hypercalcemic type (SCCOHT), and tubo-ovarian high-grade serous carcinoma (HGSC). The age of all 23 patients with DDOC/UDOC ranged between 22 and 71 years (with an average age of 50 years), and a majority of them presented with extraovarian disease (16/23). Clinical follow-up was available for 19 patients. Except for 2 patients, the remaining 17 patients died from disease, with rapid disease progression resulting in mortality within a year in stage II–IV settings (median disease-specific survival of 3 months). Eighteen of 22 cases with interpretable immunohistochemistry results showed loss of expression of core SWI/SNF protein(s) that are expected to result in SWI/SNF complex inactivation as 10 exhibited coloss of ARID1A and ARID1B, 7 loss of SMARCA4, and 1 loss of SMARCB1. Six of 23 cases were MMR-deficient. Two of 20 cases exhibited mutation-type p53 immunoreactivity. Methylation profiles showed coclustering of DDOC/UDOC with UDEC, which collectively were distinct from SCCOHT and HGSC. However, DDOC/UDOC showed an intermediate degree of copy number variation, which was slightly greater, compared with SCCOHT but much less compared with HGSC. Overall, DDOC/UDOC, like its endometrial counterpart, is highly aggressive and is characterized by frequent inactivation of core SWI/SNF complex proteins and MMR deficiency. Its molecular profile overlaps with UDEC while being distinct from SCCOHT and HGSC.