Breast Cancer Molecular Subtyping in Practice: A Real-World Study of the APIS Breast Cancer Subtyping Assay in a Consecutive Series of Breast Core Biopsies.

The APIS Breast Cancer Subtyping Kit is an mRNA-based assessment of the seven parameters including three biomarkers routinely assessed in all the newly diagnosed breast cancers (BC), oestrogen receptor (ER), progesterone receptor (PR) and HER-2 and an additional four genes that create a novel proliferation signature, MKI67, PCNA, CCNA2 and KIF23. Taken together, the data are used to produce a molecular subtype for every sample. The kit was evaluated against the current standard protocol of immunohistochemistry (IHC) and/or in situ hybridisation (ISH) in breast cancer patients. The data were presented at the weekly breast multidisciplinary team (MDT) meeting. A total of 98 consecutive cases of pre-operative breast cancer core biopsies and two core biopsies of nodal metastases yielding 100 cases were assessed. IHC and APIS results were available for 100 and 99 cases. ER was concordant in 97% cases, PR was concordant in 89% and HER-2 results were concordant with IHC/ISH in 100% of the cases. Ki-67 IHC was discordant in 3% of cases when compared with MK167 alone but discordant in 24% when compared with the four-gene proliferation signature. In conclusion, our study indicates that the APIS Breast Cancer Subtyping Kit is highly concordant when compared to the results produced for ER/PR/HER-2 by IHC and/or ISH. The assay could play a role in the routine assessment of newly diagnosed breast cancer (BC) specimens.

Concordance of HER2-low scoring in breast carcinoma among expert pathologists in the United Kingdom and the republic of Ireland -on behalf of the UK national coordinating committee for breast pathology.

BACKGROUND: Recent clinical evidence showed that breast cancer with low HER2 expression levels responded to trastuzumab deruxtecan therapy. The HER2-low cancers comprise immunohistochemistry (IHC) score 1+ and 2+ ISH non-amplified tumours, currently classified as HER2 negative. Little data exists on the reproducibility of pathologists reporting of HER2-low cancer. PATIENT AND METHODS: Sixteen expert pathologists of the UK National Coordinating Committee for Breast Pathology scored 50 digitally scanned HER2 IHC slides. The overall level of agreement, Fleiss multiple-rater kappa statistics and Cohen's Kappa were calculated. Cases with low concordance were re-scored by the same pathologists after a washout period. RESULTS: Absolute agreement was achieved in 6% of cases, all of which scored 3+. Poor agreement was found in 5/50 (10%) of cases. This was due to heterogeneous HER2 expression, cytoplasmic staining and low expression spanning the 10% cut-off value. Highest concordance (86%) was achieved when scores were clustered as 0 versus others. Improvement in kappa of overall agreement was achieved when scores 1+ and 2+ were combined. Inter-observer agreement was moderate to substantial in the whole cohort but fair to moderate in the HER2-low group. Similarly, consensus-observer agreement was substantial to almost perfect in the whole cohort and moderate to substantial in the HER2-low group. CONCLUSION: HER2-low breast cancer suffers from lower concordance among expert pathologists. While most cases can reproducibly be classified, a small proportion (10%) remained challenging. Refining the criteria for reporting and consensus scoring will help select appropriate patients for targeted therapy.

Salivary Gland Secretory Carcinoma: Clinicopathologic and Genetic Characteristics of 215 Cases and Proposal for a Grading System.

Salivary gland secretory carcinoma (SC), previously mammary analog SC, is a low-grade malignancy characterized by well-defined morphology and an immunohistochemical and genetic profile identical to SC of the breast. Translocation t(12;15)(p13;q25) resulting in the ETV6 :: NTRK3 gene fusion is a characteristic feature of SC along with S100 protein and mammaglobin immunopositivity. The spectrum of genetic alterations for SC continues to evolve. The aim of this retrospective study was to collect data of salivary gland SCs and to correlate their histologic, immunohistochemical, and molecular genetic data with clinical behavior and long-term follow-up. In this large retrospective study, we aimed to establish a histologic grading scheme and scoring system. A total of 215 cases of salivary gland SCs diagnosed between 1994 and 2021 were obtained from the tumor registries of the authors. Eighty cases were originally diagnosed as something other than SC, most frequently acinic cell carcinoma. Lymph node metastases were identified in 17.1% (20/117 cases with available data), with distant metastasis in 5.1% (6/117). Disease recurrence was seen in 15% (n=17/113 cases with available data). The molecular genetic profile showed ETV6 :: NTRK3 gene fusion in 95.4%, including 1 case with a dual fusion of ETV6 :: NTRK3 and MYB :: SMR3B . Less frequent fusion transcripts included ETV6 :: RET (n=12) and VIM :: RET (n=1). A 3-tiered grading scheme using 6 pathologic parameters (prevailing architecture, pleomorphism, tumor necrosis, perineural invasion (PNI), lymphovascular invasion (LVI), and mitotic count and/or Ki-67 labeling index) was applied. Grade 1 histology was observed in 44.7% (n=96), grade 2 in 41.9% (n=90), and grade 3 in 13.5% (n=29) of cases. Compared with low-grade and intermediate-grade SC, high-grade tumors were associated with a solid architecture, more prominent hyalinization, infiltrative tumor borders, nuclear pleomorphism, presence of PNI and/or LVI, and Ki-67 proliferative index >30%. High-grade transformation, a subset of grade 2 or 3 tumors, seen in 8.8% (n=19), was defined as an abrupt transformation of conventional SC into high-grade morphology, sheet-like growth, and a tumor lacking distinctive features of SC. Both overall survival and disease-free survival (5 and 10 y) were negatively affected by tumor grade, stage, and TNM status (each P <0.0001). SC is a low-grade malignancy with predominantly solid-microcystic growth patterns, driven by a gene fusion, most commonly ETV6 :: NTRK3 . There is a low risk for local recurrence and a good overall long-term survival, with a low risk for distant metastasis but a higher risk for locoregional lymph node metastasis. The presence of tumor necrosis, hyalinization, PNI and/or LVI, and positive resection margins correlate with higher tumor grade, less favorable prognosis, and increased mortality. The statistical results allowed us to design a 3-tiered grading system for salivary SC.

Impact of COVID-19 on the practice of breast pathologists: a survey of breast pathologists in the UK and Ireland.

AIMS: There is little information on the impact of COVID-19 on breast pathologists. This survey assessed the effect of the COVID-19 pandemic on UK and Ireland-based breast pathologists to optimise working environments and ensure preparedness for potential future pandemics. METHODS: A 35-question survey during the first wave of COVID-19 infections in the UK including questions on workload, working practices, professional development, training, health and safety and well-being was distributed to consultant breast pathologists and responses collected anonymously. RESULTS: There were 135 responses from breast pathologists based in the UK and Ireland. Most participants (75.6%) stated that their workload had decreased and their productivity dropped. 86/135 (63.7%) were given the option of working from home and 36% of those who did reported improved efficiency. Multidisciplinary team meetings largely moved to virtual platforms (77.8%) with fewer members present (41.5%). Online education, including webinars and courses, was utilised by 92.6%. 16.3% of pathologists reported shortages of masks, visors or gowns as the the most common health and safety concern. COVID-19 had a significant negative impact on the physical and mental health of 33.3% of respondents. A small number of pathologists (10.4%) were redeployed and/or retrained. CONCLUSION: The UK and Ireland breast pathologists adapted to the rapid change and maintained service delivery despite the significant impact of the pandemic on their working practices and mental health. It is important to apply flexible working patterns and environments that improve productivity and well-being. The changes suggested should be considered for long-term shaping of breast pathology services.

Sclerosing Polycystic Adenoma of Salivary Glands: A Novel Neoplasm Characterized by PI3K-AKT Pathway Alterations-New Insights Into a Challenging Entity.

Sclerosing polycystic adenoma (SPA) is a rare salivary gland neoplasm originally thought to represent a non-neoplastic lesion. Recently we have encountered an index case of apocrine intraductal carcinoma of parotid gland of 62-year-old man with invasive salivary duct carcinoma component arising from SPA, a combination of tumor entities that has never been published so far. Here, we further explore the nature of SPA by evaluating 36 cases that were identified from the authors' consultation files. The patients were 25 females and 11 males aged 11 to 79 years (mean, 47.8 y). All tumors originated from the parotid gland. Their size ranged from 11 to 70 mm (mean, 28 mm). Histologically, all cases revealed characteristic features of SPA, such as lobulated well-circumscribed growth, focal hyalinized sclerosis, presence of large acinar cells with abundant brightly eosinophilic intracytoplasmic granules, and ductal components with variable cytomorphologic characteristics, including foamy, vacuolated, apocrine, mucous, clear/ballooned, squamous, columnar and oncocyte-like cells. In all cases, there were foci of intraluminal solid and cribriform intercalated duct-like epithelial proliferations with variable dysplasia which were positive for S100 protein and SOX10, and fully enveloped by an intact layer of myoepithelial cells. In addition, 14/36 cases (39%) had focal intraductal cribriform and micropapillary apocrine-type dysplastic epithelial structures composed of cells positive for androgen receptors and negative for S100/SOX10. The intraductal proliferations of both types showed focal mild to severe dysplasia in 17 cases (17/36; 47%). Two cases showed overt malignant morphology ranging from high-grade intraductal carcinoma to invasive carcinoma with an apocrine ductal phenotype. Next generation sequencing using ArcherDX panel targeting RNA of 36 pan-cancer-related genes and/or a TruSight Oncology 170/500 Kit targeting a selection of DNA from 523 genes and RNA from 55 genes was performed. Tumor tissue was available for molecular analysis in 11 cases, and 9 (9/11; 82%) of them harbored genetic alterations in the PI3K pathway. Targeted sequencing revealed HRAS mutations c.37G>C, p.(Gly13Arg) (2 cases) and c.182A>G, p.(Gln61Arg) (2 cases), and PIK3CA mutations c.3140A>G, p.(His1047Arg) (3 cases), c.1633G>A, p.(Glu545Lys) (1 case), and c.1624G>A, p.(Glu542Lys) (1 case). Moreover, mutations in AKT1 c.49G>A, p.(Glu17Lys) and c.51dup, p.(Tyr18ValfsTer15); c.49_50delinsAG, p.(Glu17Arg) (as a double hit) were found (2 cases). In addition, germinal and somatic mutation of PTEN c.1003C>T, p.(Arg335Ter); c.445C>T, p.(Gln149Ter), respectively, were detected. Gene fusions were absent in all cases. These prevalent molecular alterations converging on one major cancer-related pathway support the notion that SPA is a true neoplasm with a significant potential to develop intraluminal epithelial proliferation with apocrine and/or intercalated duct-like phenotype. The name SPA more correctly reflects the true neoplastic nature of this enigmatic lesion.

Does Mixed Neuroendocrine-Nonneuroendocrine Neoplasm (MiNEN) of the Parathyroid Gland Exist? First Description of a Possible Case.

We describe the histological, histochemical, and immunohistochemical features of an unusual neoplasm of the parathyroid gland showing the histologic criteria of a mixed neuroendocrine-nonneuroendocrine neoplasm (MiNEN). To the best of our knowledge, this is the first report of such a tumor. A 43-year old male presented with acute and severe abdominal pain due to acute pancreatitis. On physical examination a painless lump in the right neck was detected and laboratory analyses revealed hyperparathyroidism (parathormone: 146 pmol/L, normal range 1.05-6.83) and hypercalcemia (calcium level: 3.02 mg/dL, normal range 2.25-2.5), which fell to 2.55 mg/dL after parathyroidectomy. Histologically, the tumor was a parathyroid carcinoma associated with a mucous secreting adenocarcinoma also confirmed by histochemical (Alcian blue-periodic acid Schiff) and immunohistochemical stainings. The present case expands the spectrum of MiNENs that can be found in endocrine organs.

Lobular to Lobule: Metastatic Breast Carcinoma to Olfactory Neuroblastoma.

Tumor-to-tumor metastasis (TTM) is a rare, but well-described phenomenon occurring in patients with multiple synchronous or metachronous primary malignancies. Olfactory neuroblastoma (ONB) is a rare malignant, neuroectodermal sinonasal tract tumor that occurs within the ethmoid sinus involving the cribriform plate. Very few cases of ONB have been documented to metastasize to other primary malignancies, but the reverse scenario is exceptional. During an evaluation for anosmia, a right nasal polyp was identified on imaging and endoscopy in a 66-year-old woman, with a polypectomy performed. Histologic examination showed classical features of a low-grade olfactory neuroblastoma, but within the tumor were isolated epithelioid cells which were strongly pancytokeratin immunoreactive. Review of the clinical history revealed lobular breast carcinoma treated 10 years earlier. Further evaluation with immunohistochemistry showed strong and diffuse nuclear estrogen and progesterone receptor reactivity, along with GATA3. These results confirmed TTM of an invasive lobular breast carcinoma to ONB. By employing a limited immunohistochemistry panel for all small round blue cell tumors that includes pancytokeratin, p40, S100 protein, SOX10, synaptophysin, desmin, CD99, and CD45, one is able to more accurately diagnose the classical tumor types, while also showing potentially unusual tumor features or exceptionally rare events like metastatic lobular breast carcinoma to ONB.

Extragonadal Non-gestational Choriocarcinoma with Tonsillar Presentation.

Extragonadal non-gestational choriocarcinoma is a rare but well-described phenomenon occurring in patients with midline germ cell tumors. Choriocarcinoma (ChC) is an aggressive neoplasm usually developing in women as a rare complication of pregnancy. In male patients ChC occurs in the testes, usually as a component of mixed germ cell tumors. Very few patients develop extragonadal choriocarcinoma with the tumor occurring in midline locations, such as the mediastinum, retroperitoneum, and central nervous system (mostly pineal gland). Non-midline choriocarcinoma can occur in the lung, gastrointestinal tract, and breast, sometimes blended with another primary malignancy. A midline choriocarcinoma manifesting as a head and neck malignancy is exceptional. During an evaluation of multiple enlarged cervical lymph nodes suspected to be lymphoma in a 72-year-old man, a core biopsy was taken from one of the left neck lymph nodes which histologically showed a necrotic malignancy with strong diffuse pancytokeratin staining. After an initial interpretation of metastatic carcinoma, further samples were taken from both tonsils and from a right level 5 neck lymph node. Histologically, all samples contained the same tumor, showing profound pleomorphism and multinucleated syncytial-type giant cells. A panel of immunohistochemistry studies were performed, including ß-human chorionic gonadotropin, with positive findings leading to a diagnosis of extragonadal non-gestational choriocarcinoma.

Histologic Classification and Molecular Signature of Polymorphous Adenocarcinoma (PAC) and Cribriform Adenocarcinoma of Salivary Gland (CASG): An International Interobserver Study.

Polymorphous adenocarcinoma (PAC) shows histologic diversity with streaming and targetoid features whereas cribriform adenocarcinoma of salivary gland (CASG) demonstrates predominantly cribriform and solid patterns with glomeruloid structures and optically clear nuclei. Opinions diverge on whether CASG represents a separate entity or a variant of PAC. We aimed to assess the level of agreement among 25 expert Head and Neck pathologists in classifying these tumors. Digital slides of 48 cases were reviewed and classified as: PAC, CASG, tumors with ≥50% of papillary architecture (PAP), and tumors with indeterminate features (IND). The consensus diagnoses were correlated with a previously reported molecular alteration. The consensus diagnoses were PAC in 18/48, CASG in16/48, PAP in 3/48, and IND in 11/48. There was a fair interobserver agreement in classifying the tumors (κ=0.370). The full consensus was achieved in 3 (6%) cases, all of which were classified as PAC. A moderate agreement was reached for PAC (κ=0.504) and PAP (κ=0.561), and a fair agreement was reached for CASG (κ=0.390). IND had only slight diagnostic concordance (κ=0.091). PAC predominantly harbored PRKD1 hotspot mutation, whereas CASG was associated with fusion involving PRKD1, PRKD2, or PRKD3. However, such molecular events were not exclusive as 7% of PAC had fusion and 13% of CASG had mutation. In conclusion, a fair to moderate interobserver agreement can be achieved in classifying PAC and CASG. However, a subset (23%) showed indeterminate features and was difficult to place along the morphologic spectrum of PAC/CASG among expert pathologists. This may explain the controversy in classifying these tumors.

Case Report: Colorectal cancer metastasis to a cervical lymph node - an unusual source of a neck lump.

Colorectal cancer (CRC) is the third most common cancer worldwide, and approximately 25% of patients already have metastases at the time of diagnosis. The most common metastatic sites for CRCs are the liver, lung, bone and brain and peritoneum. Cervical lymph node metastases in CRC are rare, particularly in the absence solid organ involvement. Here we present a case of a 73-year-old female patient who, following resection of a poorly differentiated caecal adenocarcinoma, re-presented four years later with a left level IV lymph node which was ultimately found to contain metastatic adenocarcinoma.

Follicular dendritic cell sarcoma presenting as a painless lump in the parotid.

Follicular dendritic cell sarcoma (FDCS) is a rare neoplasm of the antigen presenting cells of the immune system. The majority occur in lymph nodes but around 30% can occur extranodally including in the spleen, lungs, head and neck and liver. We present an unusual case of an FDCS of the parotid gland in a 51-year-old woman with a history of Hodgkin's lymphoma treated with combination chemotherapy and modified mantle radiotherapy. Only four cases of an intraparotid FDCS have been previously reported. The patient underwent a superficial parotidectomy and level 2/3 neck dissection. A diagnosis of an intraparotid FDCS (25 mm) with no nodal disease was made. Given this patient's history of radiotherapy 20 years previously, we speculate the possibility of postradiation sarcoma.

Parotid Sebaceous Carcinoma in Patient with Muir Torre Syndrome, Caused by MSH2 Mutation.

Sebaceous carcinoma of parotid gland are extremely rare with only 29 cases reported so far. The development of parotid sebaceous carcinoma in association with mutation in the mismatch repair gene that causes Muir Torre Syndrome (MTS), a subset of Lynch Syndrome, is still unclear. This study describes such a case and reviews the literature to see if an association between parotid sebaceous carcinoma and multiple visceral malignancies seen in Lynch Syndrome has ever been described. MTS represents a small subset of the Hereditary Non Polyposis Colorectal Carcinoma family, thought to be a subtype of Lynch Syndrome, where patients are prone to develop multiple visceral cancers involving gastrointestinal and genitourinary tract along with sebaceous and non-sebaceous tumours of the skin. MTS is a rare hereditary, autosomal dominant cancer syndrome caused by Microsatellite Instability and defect in DNA mismatch repair protein. The germline mutation involves mostly hMSH2 and hMLH1 genes. In MTS the skin of the head and neck area with the periocular region in particular, is affected but sebaceous carcinomas of the parotid associated with visceral malignancies has not yet been reported in literature. Here we report an index case of sebaceous carcinoma of parotid gland in a patient with MTS.

Inter- and intra-observer variability in the classification of extracapsular extension in p16 positive oropharyngeal squamous cell carcinoma nodal metastases.

OBJECTIVE: Discern inter- and intra-observer variability in the classification of extracapsular extension (ECE) in p16+ oropharyngeal (OP) SCC comparing pathologists' own criteria versus those of a well-defined classification system. METHODS: Five pathologists reviewed 50 digitally scanned nodal metastasis slides in three Rounds. Round One was by their own criteria as ECE present or absent, and Rounds Two and Three were with a defined ECE system: Grade 0 (no ECE), 0c (no ECE - thick capsule; no infiltration), 1 (ECE - cells beyond capsule), and 2 (soft tissue metastasis - cells in soft tissue without residual node). Round Three assessed intra-observer variability after an 8 month washout period. RESULTS: In Round One, all five agreed on only 48% of cases (n=24). Fleiss's Kappa value was 0.508 (95% CI: 0.357-0.644). For Rounds Two and Three, Grades 0 and 0c and Grades 1 and 2 were separately grouped as ECE absent or present. In Round Two, all five agreed on 68% of cases (n=34). Fleiss' Kappa was 0.635 (95% CI: 0.472-0.783), indicating statistically significantly better agreement. In Round Three, all five agreed on 64% of cases (n=32) giving a Fleiss's Kappa of 0.639. Pathologists agreed with their prior reads in approximately 90% of cases (average n=45.4, range n=42-49), an average intra-observer Cohen's Kappa of 0.8 (range: 0.68-0.95). Inter- and intra-observer variability rates for classification of soft tissue metastasis (ECE2) were substantially worse. CONCLUSION: There is substantial inter-, and modest intra-, observer variability among head and neck pathologists for ECE in p16+ OPSCC, which is modestly improved by a defined system.

Recent advances in the diagnostic pathology of salivary carcinomas.

This review concentrates on the most important developments since the WHO classification of 2005. In particular, the identification of specific translocations is revolutionising the way salivary tumours are considered and will have a major impact on future diagnostic practice. This is true so far in four malignancies: mammary analogue secretory, mucoepidermoid, adenoid cystic and hyalinising clear cell carcinomas. In each, the gene rearrangement is found in 80 % or more of cases. Two 2014 publications have added further possible candidates with molecular abnormalities to the list (cribriform adenocarcinoma of the tongue and minor salivary glands and epithelial-myoepithelial carcinoma), but these findings have yet to be confirmed by other investigators. The advances in molecular pathology have also allowed re-evaluation of the morphology; for example, it is now realised that the histological spectrum of hyalinising clear cell carcinoma includes intracellular mucin in over half of cases, as well as tumours with only scanty clear cells. In a separate development, it is now proposed that salivary duct carcinoma can be subdivided along molecular lines, in ways analogous to breast cancer, suggesting new therapeutic prospects in an otherwise highly aggressive malignancy.

Basal cell carcinoma metastatic to parotid gland.

Metastasis from basal cell carcinoma of the skin is very rare with cases being documented in the lymph nodes, lung, bone and parotid gland. The main histopathological differential diagnosis is the locally arising basal cell adenocarcinoma from which it is difficult to distinguish by morphology and routine immunohistochemistry. Approximately 85 % of all reported metastatic basal cell carcinomas arise in the head and neck region. Here we present a case of basal cell carcinoma of the skin of the left lateral canthus of the eye which metastasized to the intraparotid lymph nodes with infiltration of the adjacent parotid parenchyma. More awareness and vigilance is required on the part of the reporting pathologist to consider metastasis in the presence of a parotid tumour. Features favouring metastasis include history of primary cutaneous basal cell carcinoma, histological similarity to the primary lesion and absence of any demonstrable direct extension from the skin lesion. We also review the literature on metastatic basal cell carcinoma and discuss the need for adequate follow up in high risk patients.

Carcinoma ex pleomorphic adenoma, with particular emphasis on early lesions.

Carcinoma ex pleomorphic adenoma (CXPA) is a broad category of carcinomas of the salivary glands which includes at least 2 clinically relevant categories; one is referred here as early CXPA (ECXPA), the other as widely invasive CXPA. The former includes several histological patterns ranging from non-invasive/in situ/intraductal/intratubular, early invasive/extratubular/intracapsular and extracapsular (up to 6 mm). The latter includes any CXPA with invasion of >6 mm. The clinical behaviour of ECXPA is not aggressive and tends to overlap that of a pleomorphic adenoma (PA) which makes the histological report of carcinoma contradictory. These early malignant changes in PA are known since the 1970s but it has been the use of immunohistochemical and molecular genetic analysis for HER-2 and TP53 gene in the last decade that has clarified the genuine malignant nature of the cells. HER-2 and TP53 gene and protein are involved in the early stages of malignant transformation of PA. Moreover the immunohistochemical over-expression HER-2, p53 protein and Mib-1 proliferation marker may be useful markers to identify malignant areas in PA.

Delayed metastasis to the mandible of esophageal adenocarcinoma.

Around 1 % of oral cancers are metastases from distant sites. Tumor metastases to the jaw bones are uncommon and are most likely to arise from primary lung, breast, prostate or kidney tumors. Jaw bone metastases from a primary esophageal adenocarcinoma are especially rare, with only 7 reports published in the literature. Here, we describe a case of a 69 year-old male patient where 7 years elapsed between the diagnosis and successful treatment of a poorly differentiated, stage pT2N0 primary esophageal adenocarcinoma and re-presentation with jaw pain due to a metastatic mandibular deposit. The morphological appearance of the metastasis and immunohistochemical positivity with CK20, CK7 and CDX2 strongly supported an adenocarcinoma of upper gastrointestinal tract origin. This case is of particular interest as there is an unusually long time between the detection of the primary esophageal adenocarcinoma and diagnosis of metastatic disease. The longest period of time we have found for this in the literature is 9 months, although it is also reported that some oral metastases may appear more than 10 years following the primary tumor diagnosis.

Mutation profiling of adenoid cystic carcinomas from multiple anatomical sites identifies mutations in the RAS pathway, but no KIT mutations.

AIMS: The majority of adenoid cystic carcinomas (AdCCs), regardless of anatomical site, harbour the MYB-NFIB fusion gene. The aim of this study was to characterize the repertoire of somatic genetic events affecting known cancer genes in AdCCs. METHODS AND RESULTS: DNA was extracted from 13 microdissected breast AdCCs, and subjected to a mutation survey using the Sequenom OncoCarta Panel v1.0. Genes found to be mutated in any of the breast AdCCs and genes related to the same canonical molecular pathways, as well as KIT, a proto-oncogene whose protein product is expressed in AdCCs, were sequenced in an additional 68 AdCCs from various anatomical sites by Sanger sequencing. Using the Sequenom MassARRAY platform and Sanger sequencing, mutations in BRAF and HRAS were identified in three and one cases, respectively (breast, and head and neck). KIT, which has previously been reported to be mutated in AdCCs, was also investigated, but no mutations were identified. CONCLUSIONS: Our results demonstrate that mutations in genes pertaining to the canonical RAS pathway are found in a minority of AdCCs, and that activating KIT mutations are either absent or remarkably rare in these cancers, and unlikely to constitute a driver and therapeutic target for patients with AdCC.