Unmasking MASC: bringing to light the unique morphologic, immunohistochemical and genetic features of the newly recognized mammary analogue secretory carcinoma of salivary glands

Secretory carcinoma of the minor salivary gland: An in-depth case report

A 56-year-old female was referred to our service for management of a malignant salivary gland neoplasm with compromised margins that had been biopsied previously at another service. The patient reported a twenty-year history of a lesion in the oral cavity with progressive and exuberant growth over the past two years, associated with local pain and dyspnea. Physical examination revealed an erythematous, ulcerated, and hemorrhagic lesion measuring approximately 3 cm on the left soft palate and tonsillar pillar. Computed tomography revealed an expansile lesion in the topography of the left soft palate, growing predominantly toward the lumen of the nasopharynx and partially invading the left wall of this region. The patient underwent surgery and histopathologic examination revealed an infiltrative and aggressive epithelial neoplasia with large vacuolated and eosinophilic cytoplasm, vesicular nuclei, and prominent nucleoli. The neoplastic cells were arranged in a solid, microcystic, tubular, and follicular pattern with eosinophilic luminal secretion. Mitotic figures were frequent and all margins were affected by the neoplasia. Morphologic and immunohistochemical features supported the diagnosis of secretory carcinoma, and the patient is currently being followed for further therapeutic intervention.

Secretory carcinoma of parotid gland masquerading as acinic cell carcinoma on cytology: Case report and review of literature

Secretory carcinoma is a relatively recently discovered low-grade salivary gland carcinoma with morphological similarities to its breast counterpart. The histopathological features of this entity are well established; however, the cytomorphological features are not well evaluated, leading to diagnostic challenges and pitfalls. We report a case of secretory carcinoma (SC) of the parotid gland, which was misdiagnosed as acinic cell carcinoma (ACC) on fine-needle aspiration cytology, to describe the cytological features.

Salivary gland secretory carcinoma: A case presentation in minor salivary gland with review

INTRODUCTION AND IMPORTANCE

Salivary gland secretory carcinoma (SGSC) represents a rare malignant tumor of the salivary glands. Despite being regarded as low-grade tumors, they may manifest with metastases and a high-grade aggressive clinical behaviour. The literature on this subject is limited, and there is currently no standardized approach to treatment.

CASE REPORT

We report a rare case of SGSC in the palate of a 14-year-old female patient. The patient underwent excision, bilateral tonsillectomy and adjuvant radiotherapy.

CLINICAL DISCUSSION

A critical review of the literature was conducted with the objective of analysing the cases of intraoral SGSC that have been previously reported. A total of 23 articles, published between 2010 and 2024, were identified as being directly pertinent to the review, resulting in a total of 58 patients being included.

CONCLUSION

SGSC on the hard palate in a 14-year-old child is an exceedingly rare occurrence. These tumors can mimic other pathologies of the salivary glands clinically and microscopically, which can result in misdiagnosis and a delay in treatment.

Mammary analogue secretory carcinoma involving submandibular gland: Diagnostic pitfall with review of literature

ABSTRACT

Mammary analogue secretory carcinoma (MASC) is a recently defined entity among salivary gland tumors. MASC bores a striking resemblance to secretory carcinoma of breast along with the characteristics of ETV6-NTRK3 translocation. Hence, the entity was designated as MASC and was formally included in the 4th edition of World Health Organization classification of head and neck tumors in 2017. To the best of our knowledge, around 12 cases of MASC have been described in the Indian literature. MASC commonly involves parotid gland (70%). Involvement of submandibular gland is still rarer (7%). Prognosis of MASC is comparable to other low grade salivary gland malignancies; however, aggressive behavior has also been reported in few cases. This case is one of the very few reported cases describing MASC with detailed clinical, cytology, and microscopy findings along with special stains and immunohistochemistry.

Efficacy of Fine-Needle Aspiration Cytology in Diagnosing Secretory Carcinoma of Salivary Gland: A Systematic Review and Meta-Analysis

INTRODUCTION

The diagnosis of salivary gland secretory carcinoma (SC) in fine-needle aspiration specimens is challenging because its low-grade nature makes it difficult to differentiate it from various benign or malignant salivary gland neoplasms. Currently, the gold standard is demonstration of ETV6-NTRK3 fusion gene. However, the decision for ordering this costly molecular testing can be facilitated by the correct recognition of its cytomorphological features. The aim of the review was to determine the accuracy of fine-needle aspiration cytology (FNAC) in diagnosis of salivary gland SC. The secondary objective was to recognize varied cytomorphological patterns, characteristic features of SC and differentiate it from other neoplasms.

METHODS

PubMed/MEDLINE, Science Direct, Embase, Cochrane review, and PROSPERO databases were searched for studies having the following key search terms: ("secretory carcinoma of salivary gland" OR "mammary analogue secretory carcinoma of salivary gland") AND ("Cytology" OR "Cytological features" OR "aspirate" OR "cytodiagnosis") published in the time frame of 2010 to June 2023. Studies reporting cytological features of the salivary gland tumors which were confirmed/diagnosed as SC on molecular investigation, were included in the systematic review. Finally, seventeen studies reporting a total of 45 cases were included in the metanalysis.

RESULTS

The sensitivity of the FNAC in diagnosing SC in salivary gland is 27.7% (95% CI: 16.6-42.5%). The LR+ (positive likelihood ratio) was 0.654 (0.344-1.245), LR- (negative likelihood ratio) was 1.023 (0.538-1.946), and diagnostic odds ratio was 0.421 (0.129-1.374). The molecular testing and/or immunohistochemistry performed on cell block increased the diagnostic accuracy.

CONCLUSION

Recognition of subtle cytomorphological patterns, i.e., papillary formation, clusters, and singly dispersed cells along with presence of fine intracytoplasmic vacuolations were the characteristic findings in majority of cases, confirmed with diagnostic molecular profiling. This may be helpful in identification of this rare entity with limited published literature and help in increasing diagnostic accuracy.

MASC Gets UNMASKED: Visiting a Rare Tumor with Emphasis on Cytomorphological Features

Background

Secretory carcinoma (SC) is a newly described entity which has been often misdiagnosed earlier as acinic cell carcinoma on cytology. Diagnosing SC was initially based upon identifying the ETV6:NTRK3 fusion gene with the help of fluorescence in situ hybridization (FISH). Lately, with more knowledge of the reliable histomorphology, cytology, and immunohistochemistry features, definitive diagnosis can be confidently made without the help of FISH in almost every case.

Materials and Methods

Six histologically confirmed cases of SC were studied. The cytology slides of all the six cases were retrieved and reviewed to identify the characteristic features which could have helped in raising the possibility of SC on fine needle aspiration cytology itself. Cell blocks were also studied, wherever available.

Results

Patients were all male with average age of 35.2 years. The six cases in the current study demonstrated at least focal cytoplasmic vacuolization of varying sizes, papillae formations, and bland nuclear features on fine needle aspirate smears. It was also seen that S-100 and mammaglobin immunohistochemistry (IHC) are very helpful in confirming the diagnosis.

Conclusions

The results of the current study highlight the cytomorphological features which may help in clinching the diagnosis SC on cytology itself. They also highlight certain cytological features which help to rule out the other differential diagnoses.

Secretory carcinoma of major and minor salivary glands with ETV6-NTRK3 gene fusion: overcoming misdiagnosis in the era of tumour-agnostic therapy with TRK inhibitors

Introduction

Secretory carcinoma (SC) of the salivary gland is an extraordinarily rare tumour. Accurate diagnosis of SC is crucial for understanding the clinical course, prognosis, and selection of optimal therapy. The aim of this research was to analyse retrospectively the clinical and pathological characteristics of patients diagnosed with SC of the salivary gland from 2017 onwards, which aligns with its addition to the World Health Organization classification.

Material and methods

We conducted a retrospective, single-centre, clinicopathological analysis of patients diagnosed with SC of the salivary gland between 2017 and 2022. The analysis included the evaluation of NTRK3 gene rearrangements and immunohistochemical (IHC) profiling.

Results

The study included 6 patients, comprising 4 women and 2 men. The average age of the patients was 50 years (standard deviation 26). Three cases presented with tumours in the parotid gland, while one case each involved the submandibular gland, sinonasal tract, and buccal mucosa. Interestingly, despite the characteristic IHC profile, each case was initially diagnosed as a different type of salivary gland cancer. Next-generation sequencing analysis was performed in 3 cases, revealing the presence of the ETV6-NTRK3 fusion gene. This cohort notably features an intriguing case: the youngest patient documented in literature, distinguished by extended follow-up and delayed recurrence.

Conclusions

In summary, emphasizing the risk of misdiagnosis is pivotal in the context of SC of the salivary gland, which can manifest across diverse glandular sites. Accurate diagnosis, underscored by the assessment of NTRK3 gene rearrangements, assumes a critical role in guiding effective management and treatment decisions.

[New information about tumours of the salivary glands : WHO classification 2022]

The WHO 2022 classification of head and neck tumours contains another slight increase in the number of listed benign and malignant tumour entities of the salivary glands. This includes conceptual changes and alterations in the terminology of some entities. While some new features are regarded as preliminary or provisional, others are strongly disputed (for example the terminology of intraductal carcinoma). The impact of molecular findings, mainly recurrent gene fusions, continues to increase rapidly and some have been included in the definition of certain tumour entities. The significance of molecular findings is, however, still largely restricted to diagnostic aspects. Newly included entities include microsecretory carcinoma (defined by an SS18::MEF2C fusion), sclerosing microcystic adenocarcinoma (similar to skin adnexal tumours of the same name) and mucinous adenocarcinoma (characterized by AKT1 mutations with heterogeneous morphology).

Secretory carcinoma of the sinonasal cavity and pharynx: A retrospective analysis of four cases and literature review

Secretory carcinoma (SC) is a recently recognized type of salivary gland tumor characterized by t(12;15) (p13;q25) translocation resulting in an ETV6-NTRK3 gene fusion. Most SCs are located in a main salivary gland, and primary sinonasal secretary carcinoma is rare. We describe three cases of primary SC in the sinonasal cavity with high-grade transformation (HGT) in one case, and the first case in the pharynx. All tumors comprised slightly atypical cells with solid, tubular, microcystic growth patterns. The case with HGT included two components with distinct sharp boundaries and comedo necrosis, high mitotic figures and obvious cellular atypia. Tumor cells were positive for vimentin, S100, and Gata-3 and negative for p63 and DOG-1. Three cases showed nuclear staining of pan-TRK and one showed cytoplasmic staining. All cases harbored ETV6 gene rearrangement, and ETV6-NTRK3 gene fusion was detected in three cases. Most patients were treated with radical resection and adjuvant therapy. After excision, all remained tumor-free for 65-164 months (medium 98.5 months). SC in the sinonasal cavity and pharynx is a low-grade malignant tumor with histologic features overlapping those of other salivary gland tumors. Immunohistochemical analysis and fluorescence in situ hybridization are useful techniques for its differential diagnosis.

Mammary analogue secretory carcinoma presenting with cervical lymphadenopathy: A rare case report with review of the literature

Introduction

Mammary analogue secretory carcinoma is a rare malignant tumor of the salivary glands that typically involves the major glands. The aim of the current study is to report a rare case of mammary analogue secretory carcinoma that presented with left cervical lymphadenopathy.

Case report

A 59-year-old lady presented with left cervical lymphadenopathy. Tissue biopsy and immunohistochemistry revealed metastatic carcinoma, favoring ovarian origin. Staging workup was performed and, ultimately, the patient was treated as having a carcinoma of unknown primary. After showing partial response to therapy, left side neck dissection was performed. Based on better assessment of the histologic picture and a broader panel of immunohistochemistry performed on the excision specimen, the final diagnosis was that of mammary analogue secretory carcinoma.

Discussion

Mammary analogue secretory carcinoma is usually an indolent salivary gland carcinoma, with the majority of patients presenting with a slow-growing, painless mass measuring approximately 2 cm in size, and a reported duration ranging from 2 months to several years. In certain cases, pain and facial paralysis have been reported. It could also be found incidentally during radiologic assessment for thyroid illness or routine dental screening.

Conclusion

Diagnosing mammary analogue secretory carcinoma is challenging, and this should be in the differential diagnosis list of metastatic carcinomas to cervical lymph nodes.

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Mammary analogue secretory carcinoma (MASC) is a rare malignant salivary gland neoplasm.

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MASC has similar histologic and molecular characteristics to breast secretory carcinoma.

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MASC was first reported in 2010 by Skalova et al.

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In this report, a brief review regarding this condition is discussed.

Diagnosis and treatment of secretory carcinoma arising from the oral minor salivary gland: Two case reports

INTRODUCTION

Secretory carcinoma (SC) is a malignancy of the salivary glands, which is similar to SC of the breast regarding its association with neurotrophic tyrosine receptor kinase fusion-positive gene. SC is a recently described salivary gland tumor, and there are a few reports describing oral minor salivary gland-derived SC. We reported two cases of SC in the oral cavity and reviewed the literature.

PATIENT CONCERNS

The patients included a 65-year-old Japanese woman who presented with a mass of the upper lip and an 84-year-old Japanese man who presented with a mass on the buccal mucosa.

DIAGNOSIS

Diagnosis was based on histomorphological and immunohistochemical findings and identification of a specific translocation of the ETS variant 6-neurotrophic receptor tyrosine kinase 3 gene fusion. Case 1 was finally diagnosed using reverse transcription-polymerase chain reaction with formalin-fixed paraffin-embedded tissue samples, while case 2 was diagnosed using fluorescence in situ hybridization analysis.

INTERVENTIONS AND OUTCOMES

In case 1, excisional biopsy was done and there was no recurrence observed in five-year follow-up. In case 2, tumor resection was done and there was no recurrence observed in two-year follow-up.

CONCLUSION

It is highly likely for many cases of SC to be initially diagnosed as acinic cell carcinoma (AciCC) owing to their similar histological findings. The treatment strategy for minor salivary gland-originated SC is similar to that of AciCC; however, SC is often highly malignant and involves a high risk of cervical lymph node metastasis. Thus, establishing an accurate diagnosis together with pathologists and confirming the presence of the ETS variant 6-neurotrophic receptor tyrosine kinase 3 fusion gene using genetic analysis is important.

A systematic review of secretory carcinoma of the salivary gland: where are we?

OBJECTIVE

The aim of this systematic review was to describe the epidemiology, diagnostic criteria, differential diagnosis, treatment, prognostic factors, and treatment outcomes of secretory carcinoma.

STUDY DESIGN

A comprehensive search of Lilacs, PubMed, Science Direct, and Web of Science databases was conducted to identify all case reports, letter to the editor, and histopathologic reclassifications regarding salivary gland secretory carcinoma published in English, Spanish, French, and Portuguese.

RESULTS

The final analysis included 119 studies, which totaled 642 secretory carcinoma diagnoses, with 239 case reports and 403 diagnostic reclassifications, mostly in the United States. The age range was 5 to 87 years, and cases were predominantly in males (58.7%) and mostly affecting the parotid glands (73.7%). The disease usually presents as a slow-growing, painless mass. The main differential diagnosis is acinic cell carcinoma, and the tumor is usually treated with surgery. The prognosis is considered favorable, although there have been reports of local recurrences, distant metastases, and deaths.

CONCLUSIONS

It is important that clinicians become aware of this salivary gland neoplasm and report clinical data, clinical course, management and long-term follow-up. There is an urgent need to conduct more clinical trials, especially on tropomyosin receptor kinase (TRK) inhibitors and other potential target therapy modalities.

Secretory Carcinoma of the Salivary Gland - Systematic Review of the Literature and Report of 2 Cases

PURPOSE

Secretory carcinoma (SC) of the salivary gland, formerly known as mammary analogue secretory carcinoma, is an uncommon and fairly newly described low grade malignant neoplasm of the salivary gland. Given the small number of cases reported in the literature to date, treatment guidelines are scarce. This study aimed to describe the clinical characteristics of SC, discuss prior management strategies, and provide recommendations for future treatment.

METHODS

We performed a systematic review of all the cases of SC reported in the literature since it was first recognized in 2010. Using Pubmed, Crossref, and Google Scholar, we identified all articles reporting cases of SC.

RESULTS

We identified 657 cases of SC in 109 articles. In addition, we provided 2 new cases, for a total of 659 cases in 110 articles. To our knowledge, this is the largest review of cases of SC in the literature to date. We summarized the clinical characteristics of SC, as well as the nodal status, clinical management, recurrence rate, and death rate.

CONCLUSIONS

SC occurs on average in middle age (with a large age range), presents most often initially as localized disease without metastasis, and has a low but not insignificant recurrence rate. Deaths have been reported. The generalized recommendations for treatment of SC are in line with those of other low-grade salivary gland malignancies.

Diagnostic challenges and successful organ-preserving therapy in a case of secretory carcinoma of minor salivary glands

BACKGROUND

Secretory carcinoma is a more recently described subtype of salivary gland carcinoma that may pose diagnostic challenges and frequently harbors NTRK fusions that may successfully be targeted by TRK inhibitors in advanced disease.

CASE

We present the case of a female patient with secretory carcinoma arising in the base of tongue with persistent disease after debulking surgery and definitive chemoradiation. As an alternative to salvage surgery, which would have resulted in significant impairment of swallowing and speech function, a targeted therapy with the TRK-inhibitor larotrectinib against an identified ETV6-NTRK3 fusion product was initiated. Larotrectinib treatment has been well tolerated, resulted in durable complete response and the patient maintains good swallowing and speech function.

CONCLUSION

The presented case underscores the importance of the accurate diagnosis of secretory carcinoma. It further highlights the impact of molecular testing as targeted therapies may play an important role in the management of advanced salivary gland cancers.

A case report of surgical resection of secretory carcinoma in the maxillary and ethmoid sinus

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Mammary Analogue Secretory Carcinoma (MASC) is a head and neck tumour that was first defined in 2010.

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Only two cases of Secretory Carcinoma have reported in the sinuses.

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We present a case of a Secretory Carcinoma presenting in the maxillary and ethmoid sinuses.

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The tumour treated with surgical resection and re-resection and was disease free at 1 year follow up.

Introduction

Secretory Carcinoma is a recently discovered head and neck tumour. Surgical resection is generally the first line of treatment with neck dissection, radiation, and chemotherapy decided based on clinical, radiological, and histological parameters. We present a case of a Secretory Carcinoma presenting in the maxillary and ethmoid sinuses.

Case

A 39-year-old male presented with left nasal obstruction and chronic rhinosinusitis beginning after surgical repair of the mandible and maxilla due to facial trauma. A CT scan of the head showed soft tissue density in the left maxillary sinus extending through the ethmoid sinus and posterior nasal cavity. Functional endoscopic sinus surgery (FESS) was performed to remove the obstructing lesion. Biopsy was analysed and the main differential diagnosis was between a non-intestinal type adenocarcinoma of nasal origin and a salivary carcinoma.

Discussion

To our knowledge, there have only been two cases of Secretory Carcinoma reported in the sinuses: one case in the ethmoid sinus and the other in the maxillary sinus. This is the first to report follow up at 1 year.

Conclusion

Both MRI and exam showed no evidence of recurrent disease at one year follow up. This report aims to further the understanding of Secretory Carcinoma tumours in the sinuses. Our report could be used to further understand diagnostic criteria for Secretory Carcinoma in the sinuses as well as treatment outcomes for surgical resection without adjuvant treatment.

Genomic Analysis of Salivary Gland Cancer and Treatment of Salivary Gland Cancers

Salivary gland cancer is a heterogenous group of tumors that presents challenges with both diagnosis and therapy. Recent advances in the classification of salivary gland cancers have led to distinct histologic and genomic criteria that successfully differentiate between cancers with similar clinical behavior and appearance. Genomic abnormalities have led to the emergence of targeted therapies being used in their therapy with drastic improvements in outcomes as well as reductions in treatment-related toxicity. Dramatic results seen with molecular targets, such as HER2, TRK, and others, indicate that this approach has the potential to yield even better treatments for the future.

Expanding the Molecular Spectrum of Secretory Carcinoma of Salivary Glands With a Novel VIM-RET Fusion

BACKGROUND

Secretory carcinoma (SC), originally described as mammary analogue SC, is a predominantly low-grade salivary gland neoplasm characterized by a recurrent t(12;15)(p13;q25) translocation, resulting in ETV6-NTRK3 gene fusion. Recently, alternative ETV6-RET, ETV6-MAML3, and ETV6-MET fusions have been found in a subset of SCs lacking the classic ETV6-NTRK3 fusion transcript, but still harboring ETV6 gene rearrangements.

DESIGN

Forty-nine cases of SC revealing typical histomorphology and immunoprofile were analyzed by next-generation sequencing using the FusionPlex Solid Tumor kit (ArcherDX). All 49 cases of SC were also tested for ETV6, RET, and NTRK3 break by fluorescence in situ hybridization and for the common ETV6-NTRK3 fusions using reverse transcription polymerase chain reaction.

RESULTS

Of the 49 cases studied, 37 (76%) occurred in the parotid gland, 7 (14%) in the submandibular gland, 2 (4%) in the minor salivary glands, and 1 (2%) each in the nasal mucosa, facial skin, and thyroid gland. SCs were diagnosed more frequently in males (27/49 cases; 55%). Patients' age at diagnosis varied from 15 to 80 years, with a mean age of 49.9 years. By molecular analysis, 40 cases (82%) presented the classic ETV6-NTRK3 fusion, whereas 9 cases (18%) revealed an alternate fusion. Of the 9 cases negative for the ETV6-NTRK3 fusion, 8 cases presented with ETV6-RET fusion. In the 1 remaining case in the parotid gland, next-generation sequencing analysis identified a novel VIM-RET fusion transcript. In addition, the analysis indicated that 1 recurrent high-grade case in the submandibular gland was positive for both ETV6-NTRK3 and MYB-SMR3B fusion transcripts.

CONCLUSIONS

A novel finding in our study was the discovery of a VIM-RET fusion in 1 patient with SC of the parotid gland who could possibly benefit from RET-targeted therapy. In addition, 1 recurrent high-grade case was shown to harbor 2 different fusions, namely, ETV6-NTRK3 and MYB-SMR3B. The expanded molecular spectrum provides a novel insight into SC oncogenesis and carries important implications for molecular diagnostics, as this is the first SC-associated translocation with a non-ETV6 5' fusion partner. This finding further expands the definition of SC while carrying implications for selecting the appropriate targeted therapy.

Atypical Presentation of Mammary Analogue Secretory Carcinoma of the Lip

Mammary analogue secretory carcinoma (MASC) of the salivary gland is a rare tumor that was first described by Skalova et al in 2010, and since then, only a few hundred cases have been reported in the literature. Prior to Skalova's report, MASC was histologically misclassified as acinic cell carcinoma (ACC), pleomorphic adenoma, mucoepidermoid carcinoma, or adenocarcinoma, not otherwise specified. Mammary analogue secretory carcinoma has a low incidence rate overall, accounting for less than 0.3% of all salivary gland tumors. Histopathologic and cytogenic analysis of MASC is identical to secretory carcinoma of the breast, leading to the proposed name by Skalova. The purpose of this case presentation is to describe an atypical presentation of MASC, to compare this case with the classic description of MASC, and to contrast the various features of MASC to ACC in order to improve the accuracy of future diagnoses and help guide treatment.

A case of secretory carcinoma of the submandibular gland with unusual immunohistochemical staining

Mammaglobin negative secretory carcinoma may be overlooked. It is important to assess the possibility of diagnosis when histology is suggestive and immunohistochemical staining for S-100 is positive even when staining for mammaglobin is negative.

Secretory Carcinoma of Salivary Gland with High-Grade Histology Arising in Hard Palate: A Case Report

Secretory carcinoma (SC) is a recently described salivary gland tumor reported in the fourth edition of World Health Organization classification of head and neck tumors. SC is characterized by strong S-100 protein, mammaglobin, and vimentin immunoexpression, and harbors a t(12;15)(p13;q25) translocation which leads to ETV6-NTRK3 fusion product. Histologically, SC displays a lobulated growth pattern and is often composed of microcystic, tubular, and solid structures with abundant eosinophilic homogenous or bubbly secretion. SC is generally recognized as low-grade malignancy with low-grade histopathologic features, and metastasis is relatively uncommon. In this case, we described a SC of hard palate that underwent high grade transformation and metastasis to the cervical lymph node in a 54-year-old patient. In addition, this case showed different histological findings between primary lesion and metastasis lesion. Therefore, the diagnosis was confirmed by the presence of ETV6 translocation. Here, we report a case that occurred SC with high-grade transformation in the palate, and a review of the relevant literature is also presented.

Larotrectinib, a selective tropomyosin receptor kinase inhibitor for adult and pediatric tropomyosin receptor kinase fusion cancers

Gene fusions involving NTRK1, NTRK2 and NTRK3 are oncogenic drivers across a wide variety of cancer types. Inhibitors of the chimeric TRKA/B/C protein kinases encoded by these fusions are now available, including larotrectinib, a potent and highly selective oral drug. Integrated data from three trials demonstrate substantial clinical activity of larotrectinib in patients with many different types of cancers harboring NTRK fusions. Larotrectinib has received accelerated approval from both the US FDA and the EMA. Resistance mutations have been observed in the kinase domains of the NTRK fusion genes and development of next-generation tropomyosin receptor kinase inhibitors designed to overcome such resistance mutations is being actively pursued in clinical trials and ongoing drug discovery efforts.

The HTN3-MSANTD3 Fusion Gene Defines a Subset of Acinic Cell Carcinoma of the Salivary Gland

The spectrum of tumors arising in the salivary glands is wide and has recently been shown to harbor a network of tumor-specific fusion genes. Acinic cell carcinoma (AciCC) is one of the more frequently encountered types of salivary gland carcinoma, but it has remained a genetic orphan until recently when a fusion between the HTN3 and MSANTD3 genes was described in one case. Neither of these 2 genes is known to be implicated in any other malignancy. This study was undertaken to investigate whether the HTN3-MSANTD3 fusion is a recurrent genetic event in AciCC and whether it is a characteristic of one of its histological variants. Of the 273 AciCCs screened, 9 cases showed rearrangement of MSANTD3 by break-apart fluorescence in situ hybridization, 2 had 1 to 2 extra signals, and 1 had gain, giving a total of 4.4% with MSANTD3 aberrations. In 6 of 7 available cases with MSANTD3 rearrangement, the HTN3-MSANTD3 fusion transcript was demonstrated with real-time polymerase chain reaction. Histologically, all fusion-positive cases were predominantly composed of serous tumor cells growing in solid sheets, with serous tumor cells expressing DOG-1 and the intercalated duct-like cell component being CK7 positive and S-100 positive in 6/9 cases. All but one case arose in the parotid gland, and none of the patients experienced a recurrence during follow-up. In contrast, the case with MSANTD3 gain metastasized to the cervical lymph nodes and lungs. In conclusion, we find the HTN3-MSANTD3 gene fusion to be a recurrent event in AciCC with prominent serous differentiation and an indolent clinical course.

Mammary analogue secretory carcinoma of the minor salivary gland: report of two cases

Mammary analogue secretory carcinoma (MASC) is a recently described salivary gland tumour notable for a balanced chromosomal translocation t(12;15)(p13;q25) that contributes to ETV6 gene rearrangements. It was first reported in 2010 by Skalova et al. with histological features resembling secretory carcinoma of the breast and was acknowledged and referred to as "secretory carcinoma" in the updated 2017 WHO classification. It is reported that MASC accounts for <0.3% of all salivary gland tumours, with a finite number of published reports on it. MASC has a range of histological features and clinical behaviours. The histopathological diagnosis of MASC can be difficult with current immunohistochemical methods. One case was located in the left palate, and 1 case was located in the soft palate. The maximum diameter of the tumour was 1.4~3.7 cm. CT demonstrated a mass that had not invaded into the palate bone, and the patients underwent palate neoplasm expanded ectomy without neck dissection or postoperative radiation therapy. Histopathological examination revealed that the tumour cells consisted of a mixed arrangement of microcystic, papillary-cystic, follicular, and solid lobular growth patterns. Eosinophilic cytoplasm and intraluminal or intracytoplasmic colloid-like secretions were observed. The final pathology confirmed the diagnosis of MASC with immunohistochemically neoplastic cells staining positive for S-100 and mammaglobin. The patients were asymptomatic at their 12-month follow up. More studies are needed to identify the typical behaviour of this tumour and establish the standard treatment regimen. This study aims to reinforce the awareness of this tumour by analysing its clinicopathologic features, immunophenotype, and diagnosis.

Ancillary testing in salivary gland cytology: A practical guide

Salivary gland cytology is challenging, and historically the role of ancillary testing has been limited. However, numerous molecular/genetic advances in the understanding of salivary gland neoplasms during the last decade have facilitated the development of many useful diagnostic markers, such as PLAG1 and HMGA2 immunohistochemistry for pleomorphic adenoma and ETV6 fluorescence in situ hybridization for secretory carcinoma. Numerous salivary gland neoplasms are characterized by specific molecular/genetic alterations, many of which can be identified on cytologic preparations by karyotype analysis, fluorescence in situ hybridization, or immunohistochemical surrogates. Next-generation sequencing also has potential diagnostic applications, although to the authors' knowledge it currently has no routine role in salivary cytology. The primary goal of salivary fine-needle aspiration (FNA) is to facilitate appropriate clinical management. Ancillary testing has greatly enhanced the ability for accurate classification as per The Milan System for Reporting Salivary Gland Cytopathology and allows for the definitive diagnosis of many salivary FNA specimens, and also may resolve diagnostic uncertainty for FNAs that may be classified in The Milan System for Reporting Salivary Gland Cytopathology categories of salivary gland neoplasm of uncertain malignant potential or suspicious for malignancy. This review provides an updated discussion of the molecular/genetic features of the more commonly encountered salivary neoplasms by FNA, and discusses the application of available diagnostic immunohistochemical and molecular tests in salivary gland cytology.

[Immunophenotyping of lung tumors : An update]

The WHO Classification of Lung Tumors (2015) established the use of immunohistochemical stainings for resection specimens, however, detailed recommendations had been missing. Now, an international expert panel has summarized key questions for daily routine practice and provided recommendations to assist the community in the appropriate use of immunohistochemistry in this context. This article provides an overview of the most important aspects.

Mammary Analog Secretory Carcinoma of the Nasal Cavity: Characterization of 2 Cases and Their Distinction From Other Low-grade Sinonasal Adenocarcinomas

Secretory carcinoma, originally described as mammary analog secretory carcinoma (MASC), is a low-grade salivary gland tumor characterized by a t(12;15)(p13;q25) translocation, resulting in an ETV6-NTRK3 gene fusion. Most MASCs are localized to the parotid gland and intraoral minor salivary glands. Moreover, ETV6-rearranged carcinomas with secretory features have been reported recently in the thyroid (with and without a history of radiation exposure), skin, and in very rare instances in the sinonasal tract. Here, we describe 2 cases of primary MASC in the sinonasal tract and provide a detailed clinical and histopathologic characterization of their morphology, immunohistochemical profile, and genetic background and highlight features allowing for its separation from its recently described molecular mimicker, ETV6-rearranged low-grade sinonasal adenocarcinoma.

Mammary analogue secretory carcinoma presenting as a cystic parotid mass

We present a case of a 63-year-old male with an 8-year history of a left-sided cystic facial mass which recurred despite multiple drainage procedures. Imaging findings showed a cystic mass in the left parotid gland and it was surgically resected. Pathology confirmed it to represent a mammary analogue secretory carcinoma, a relatively newly described entity. This case illustrates that mammary analogue secretory carcinoma can masquerade as a cyst within the parotid gland.

The significance of the morphological and immunological characteristics in the diagnosis of parotid mammary analogue secretory carcinoma: five case reports and a review of the literature

Mammary analogue secretory carcinoma (MASC) of the salivary glands is rarely reported. In this article, the histopathological features of 5 cases of parotid MASC were retrospectively analyzed. AB/PAS and immunohistochemical staining of S-100, mammaglobin and P63 was performed, which were validated by the ETV6-fluorescent FISH detection of NTRK3 gene. The tumors were composed of two kinds of tumor cells. One kind of cells was rich in cytoplasms, transparent or vacuole-like, partial basophilic double tropism, but another type of cellular cytoplasm was acidophilic. The karyotype was consistent between two types of tumors in the vacuolar pattern. Although the tumor cells were arranged in different forms, the cystic (capsule or microcapsule) structures were constantly observed. Two kinds of tumor cells produced different secretions, which were distributed among the tumor cells. Tumor tissues were divided by hardened collagen interstitial, even in the infiltration lesion, collagen and tumor cells mass was also inseparable. The expression of mammaglobin and S-100 significantly differed between the two types of tumor cells. These characteristics contribute to the differential diagnosis of MASC. ETV6-NTRK3 gene detection can be applied in the diagnosis of atypical cases, but it should not be done routinely.

The key radiologic and cytomorphologic features of oncocytic and oncocytoid lesions of the salivary gland

Oncocytic and oncocytoid lesions represent a distinct subset of salivary gland lesions. True oncocytic lesions of the salivary gland are entirely composed of oncocytes. These are characterized by the presence of abundant eosinophilic granules due to the presence of abundant cytoplasmic mitochondria. Oncocytic lesions of the salivary gland include oncocytosis, oncocytoma, and oncocytic carcinoma. In addition to the true oncocytic lesion, there exists another group of salivary gland lesions, which demonstrate cells with abundant and occasionally granular cytoplasm. These are often termed as "oncocytoid" lesions. The recently proposed Milan System for reporting salivary gland cytology clearly states that fine-needle aspiration specimens representing oncocytic/oncocytoid lesions of salivary gland cannot effectively distinguish between a nonneoplastic lesion, benign and malignant neoplasms. Therefore, most lesions lacking classic cytomorphologic features will be classified under the umbrella diagnostic term of "Salivary Gland Neoplasm of Uncertain Malignant Potential" (SUMP). In this review, we discuss and illustrate key clinicopathologic and radiologic features that can help the practicing cytopathologist narrow down the differential and provide the best management based diagnosis.

Salivary Gland Malignancies

Salivary gland tumors are rare pathologic entities that are derived from major and minor salivary gland tissue located throughout the head and neck region. These tumors are distinctly heterogenous, comprising numerous cell types, especially those deemed malignant. The incidence of malignant salivary gland tumors is widely distributed in both adult and pediatric patient populations. Accurate diagnosis and optimal treatment of these tumors pose challenges to both interpreting pathologists and ablative surgeons. This article examines the epidemiology and pathology of malignant tumors of the major and minor salivary glands and provides recommendations for the most successful treatment approaches.

Best Practices Recommendations for Diagnostic Immunohistochemistry in Lung Cancer

Since the 2015 WHO classification was introduced into clinical practice, immunohistochemistry (IHC) has figured prominently in lung cancer diagnosis. In addition to distinction of small cell versus non-small cell carcinoma, patients' treatment of choice is directly linked to histologic subtypes of non-small cell carcinoma, which pertains to IHC results, particularly for poorly differentiated tumors. The use of IHC has improved diagnostic accuracy in the classification of lung carcinoma, but the interpretation of IHC results remains challenging in some instances. Also, pathologists must be aware of many interpretation pitfalls, and the use of IHC should be efficient to spare the tissue for molecular testing. The International Association for the Study of Lung Cancer Pathology Committee received questions on practical application and interpretation of IHC in lung cancer diagnosis. After discussions in several International Association for the Study of Lung Cancer Pathology Committee meetings, the issues and caveats were summarized in terms of 11 key questions covering common and important diagnostic situations in a daily clinical practice with some relevant challenging queries. The questions cover topics such as the best IHC markers for distinguishing NSCLC subtypes, differences in thyroid transcription factor 1 clones, and the utility of IHC in diagnosing uncommon subtypes of lung cancer and distinguishing primary from metastatic tumors. This article provides answers and explanations for the key questions about the use of IHC in diagnosis of lung carcinoma, representing viewpoints of experts in thoracic pathology that should assist the community in the appropriate use of IHC in diagnostic pathology.

Mammary Analogue Secretory Carcinoma of the Palate: Case Report and Review of the Literature

Mammary analogue secretory carcinoma (MASC) is a recently described salivary gland tumor, with a limited number of published reports. Less than three hundred cases have been reported in the literature and only 18 of these cases have been reported in minor palatal salivary glands, though publication bias is likely a factor. We present a case of a 57-year-old male who was diagnosed with MASC tumor presenting in a minor salivary gland and briefly review the current literature. MASC has a variety of histological features and different range of clinical behaviors. The histopathological diagnosis of MASC can be difficult, and the immunohistochemical profile of MASC is still being updated. The gold standard for MASC diagnosis is cytogenetics, with the majority having a translocation t(12;15)(p133;q25). Presently, there is no conclusive evidence that MASC should be treated differently than any other low-grade malignant salivary gland tumors, though high-grade transformation has been described.

The Role of Molecular Testing in the Differential Diagnosis of Salivary Gland Carcinomas

Salivary gland neoplasms are a morphologically heterogenous group of lesions that are often diagnostically challenging. In recent years, considerable progress in salivary gland taxonomy has been reached by the discovery of tumor type-specific fusion oncogenes generated by chromosome translocations. This review describes the clinicopathologic features of a selected group of salivary gland carcinomas with a focus on their distinctive genomic characteristics. Mammary analog secretory carcinoma is a recently described entity characterized by a t(12;15)(p13;q25) translocation resulting in an ETV6-NTRK3 fusion. Hyalinizing clear cell carcinoma is a low-grade tumor with infrequent nodal and distant metastasis, recently shown to harbor an EWSR1-ATF1 gene fusion. The CRTC1-MAML2 fusion gene resulting from a t(11;19)(q21;p13) translocation, is now known to be a feature of both low-grade and high-grade mucoepidermoid carcinomas associated with improved survival. A t(6;9)(q22-23;p23-34) translocation resulting in a MYB-NFIB gene fusion has been identified in the majority of adenoid cystic carcinomas. Polymorphous (low-grade) adenocarcinoma and cribriform adenocarcinoma of (minor) salivary gland origin are related entities with partly differing clinicopathologic and genomic profiles; they are the subject of an ongoing taxonomic debate. Polymorphous (low-grade) adenocarcinomas are characterized by hot spot point E710D mutations in the PRKD1 gene, whereas cribriform adenocarcinoma of (minor) salivary glands origin are characterized by translocations involving the PRKD1-3 genes. Salivary duct carcinoma (SDC) is a high-grade adenocarcinoma with morphologic and molecular features akin to invasive ductal carcinoma of the breast, including HER2 gene amplification, mutations of TP53, PIK3CA, and HRAS and loss or mutation of PTEN. Notably, a recurrent NCOA4-RET fusion has also been found in SDC. A subset of SDC with apocrine morphology is associated with overexpression of androgen receptors. As these genetic aberrations are recurrent they serve as powerful diagnostic tools in salivary gland tumor diagnosis, and therefore also in refinement of salivary gland cancer classification. Moreover, they are promising as prognostic biomarkers and targets of therapy.

Novel gene fusions in secretory carcinoma of the salivary glands: enlarging the ETV6 family

Secretory carcinoma (SC) of the salivary gland is a low-grade malignancy associated with a well-defined clinical, histologic, immunohistochemical, and cytogenetic signature. Although the t(12;15) (p13;q25) translocation resulting in an ETV6-NTRK3 gene fusion is well documented, advances in molecular profiling in salivary gland tumors have led to the discovery of RET as another ETV6 gene fusion partner in SC. Here, we applied an RNA-based next-generation sequencing (NGS) approach for fusion detection on 14 presumed SC. The cases included 7 SC with classic ETV6-NTRK3 gene fusion and 3 SC harboring ETV6-RET gene fusion. In addition, 2 cases revealed a NCOA4-RET gene fusion and were subsequently reclassified as intraductal carcinomas. One case with an unusual dual-pattern morphology revealed a novel translocation involving ETV6, NTRK3, and MAML3 gene rearrangements. Interestingly, no ETV6-NTRK3 or ETV6-RET SC was ever documented to have this unique dual-pattern morphology or harbor a MAML3 mutation. The remaining case had no detected chromosomal abnormalities. Advances in molecular profiling of SC have led to the discovery of novel fusion partners such as RET and now MAML3. Further molecular characterization of salivary gland neoplasms is needed as these mutations may present alternative therapeutic targets in patients with these tumors.

Secretory carcinoma of the major salivary gland: Provincial population-based analysis of clinical behavior and outcomes

BACKGROUND

Our aim was to identify the number of cases of secretory carcinoma (SC) of the major salivary gland in a population-based cohort and review its clinical behavior with long-term follow-up.

METHODS

All malignant salivary gland tumors (MSGTs) diagnosed between 1980 and 2014 were assessed for histological features compatible with SC and 140 were selected for further analysis.

RESULTS

Twenty two new cases of SC were identified, 19 of which were originally classified as acinic cell carcinoma, and 3 as adenocarcinoma, not otherwise specified (NOS). Lymph node involvement was less common in SC tumors (5%) than in the control group (11%). Disease recurrence was seen less frequently in SC (9%) than the control group (20%). Mean disease-free survival was 192 months for SC compared with 162 months for controls (P = 0.15).

CONCLUSION

The clinical course of SC is typically indolent with a low risk of relapse not significantly different from other low-grade MSGT.

Secretory Carcinoma of the Thyroid Gland: Report of a Highly Aggressive Case Clinically Mimicking Undifferentiated Carcinoma and Review of the Literature

After being described in the salivary glands as a malignancy with features essentially identical to those of the breast, secretory carcinoma (SC) (formerly mammary analogue SC) has now been identified in other sites including the skin, lung, and thyroid gland. In the breast, SC has a relatively favorable prognosis. Likewise when arising in the salivary glands, it is generally considered to be a low to intermediate grade carcinoma; however, there is a range of clinical behavior with occasional patients dying of progressive disease. SCs of the thyroid gland are rare, and reports suggest a relatively aggressive behavior, at least relative to well differentiated carcinomas such as papillary carcinoma and minimally invasive follicular carcinoma. We present a patient with a highly aggressive thyroid gland SC that mimicked undifferentiated carcinoma clinically. The patient had widespread metastatic disease and died rapidly from airway compromise. We also review the literature for reported cases of thyroid gland SC in order to better establish the clinical features and expected clinical course of such tumors occurring at this site.

Salivary gland tumors: Molecular characterization and therapeutic advances for metastatic disease

Salivary gland cancers represent a rare group of tumors composed by over 20 histological subtypes. Initially treated as one single disease, its diagnosis, prognosis, and treatment are currently being stratified based on morphology. More recently, insight has been provided on the molecular characterization of each subtype, further improving diagnostic accuracy and paving the way for personalized therapy. In this article, we provide a comprehensive review of recent breakthroughs, preliminary results of novel therapy, and future directions on the treatment of these complex malignancies.

Synchronous Parotid (Mammary Analog) Secretory Carcinoma and Acinic Cell Carcinoma: Report of a Case

Mammary analogue secretory carcinoma (MASC) is a recently described low-grade salivary gland malignancy with histologic, immunohistochemical and molecular similarities to secretory carcinoma of the breast, including a specific t(12;15)(p13;q25) resulting in an ETV6-NTRK3 gene fusion. Ultrasound and magnetic resonance imaging frequently document a macrocystic structure. The main differential diagnosis of secretory carcinoma is with low grade acinic cell carcinoma (AciCC). The two can be differentiated with immunohistochemical stains for S100, mammaglobin, carbonic anhydrase VI and DOG-1; the identification of the specific translocation can help to characterize non-typical cases. We report a unique case of synchronous MASC and AciCC presenting in a parotid gland and discuss the implications of the correct identification of the two tumors.

Primary mammary analogue secretory carcinoma of the lung: a case report

Mammary analogue secretory carcinoma (MASC) is a recently discovered salivary gland tumor described mostly in the major salivary glands and occasionally in the skin. We report a primary endobronchial tumor with histology, immunophenotype, and ETV6 rearrangement characteristic of MASC in a 62-year-old woman. The diagnosis was initially made on a transbronchial biopsy with fluorescence in situ hybridization confirmation of ETV6 rearrangement. The patient underwent lobectomy demonstrating a large endobronchial mass. To our knowledge, this is the first report of MASC arising as a primary pulmonary tumor. This tumor was unusual in that it is the largest (8.5 cm) MASC ever reported, showed an increased mitotic count (6/10 high-power fields) without high-grade cytology, and presented with advanced-stage disease that included visceral pleural invasion and lymph node metastasis.

Molecular Profiling of Mammary Analog Secretory Carcinoma Revealed a Subset of Tumors Harboring a Novel ETV6-RET Translocation: Report of 10 Cases

ETV6 gene abnormalities are well described in tumor pathology. Many fusion partners of ETV6 have been reported in a variety of epithelial, mesenchymal, and hematological malignancies. In salivary gland tumor pathology, however, the ETV6-NTRK3 translocation is specific for (mammary analog) secretory carcinoma, and has not been documented in any other salivary tumor type. The present study comprised a clinical, histologic, and molecular analysis of 10 cases of secretory carcinoma, with typical morphology and immunoprofile harboring a novel ETV6-RET translocation.

Diagnostic Approaches for Salivary Gland Tumors with Secretory and Microcystic Features

Secretory carcinoma (SC) of the salivary gland is a new entity that shares the unique morphologic features and cytogenetic characteristics of the ETV6-NTRK3 fusion gene with its breast counterpart. Before identification of SC of the salivary gland, it was most frequently diagnosed as acinic cell carcinoma (AciCC). We retrospectively reviewed our own database of salivary gland tumors harboring microcystic and papillary architecture and/or secretory features that were originally diagnosed as AciCC. We selected nine cases of AciCC showing diffuse S-100 expression on immunohistochemistry (IHC). A recently diagnosed case of SC was included in the study as a reference sample. We performed IHC of S-100 and mammaglobin and ETV6 gene fluorescence in situ hybridization (FISH) in all cases. Seven cases were positive for both S-100 and mammaglobin, while five of the seven (71.4%) demonstrated ETV6 gene translocation by FISH. In the cases which did not co-express either S-100 or mammaglobin on IHC, ETV6 gene rearrangement was not shown on FISH. In conclusion, if a salivary gland tumor has morphologic features of SC with co-expression of S-100 and mammaglobin, ETV6 FISH can be performed to confirm the diagnosis of SC of the salivary gland.

Mammary analogue secretory carcinoma of salivary glands: diagnostic pitfall with distinct immunohistochemical profile and molecular features

Mammary analogue secretory carcinoma (MASC) is a newly defined entity among salivary gland malignancies which has just been established in the 4^th edition of the WHO classification of head and neck tumors. MASC (synonym: secretory carcinoma) are characterized by a specific rearangement of the ETV6 gene locus. Here, we present a series of 3 MASC cases including clinical data with follow-up for up to 26 months. All tumours immunhistochemically displayed strong positivity for cytokeratin 7, and mammaglobin, focal positivity for S100, cytokeratin 5/6 and muc-4. In contrast, immunhistochemical stainings against cytokeratin 14, hormon receptors, Her2/neu, androgen receptor and prostate-specific antigen were consistently negative. FISH analysis showed translocation of the ETV6 gene locus in the majority of tumour cell nuclei. During clinical follow-up, no local relapse or metastasis was detected. As these carcinomas are clinically and radiologically indistinguishable from other salivary gland tumours and as therapeutic approaches and prognosis might differ, we need to be able to diagnose MASC correctly.

Clinicopathologic and molecular characterization of mammary analogue secretory carcinoma of salivary gland origin

BACKGROUND

Mammary analogue secretory carcinoma (MASC) is a newly recognized salivary gland tumor that harbors a characteristic balanced chromosomal translocation t (12; 15) (p13; q25) resulting in an ETV6-NTRK3 fusion gene.

METHODS

Retrospective study of 111 salivary gland carcinomas revealed 37 cases with secretory features and growth patterns resembling secretory carcinoma of breast. These 37 cases were originally diagnosed as acinic cell carcinoma, adenocarcinoma not otherwise specified and cystadenocarcinoma. Positive immunostaining for S-100 protein and mammaglobin, followed by detection of ETV6 gene rearrangement by FISH and/or ETV6-NTRK3 fusion transcript by RT-PCR were used to identify MASCs.

RESULTS

In the cohort of 37 salivary carcinomas with secretory features we have identified 10 cases of MASC. All 10 MASCs were positive for mammaglobin, S-100 protein and SOX10, while staining for DOG1 and p63 protein were mostly absent. In 7/10 cases, both FISH and RT-PCR were positive while three remaining cases showed break of ETV6 gene by FISH analysis and the RT-PCR was negative. Clinical follow-up data were obtained in 6 out of 10 patients with MASC. In 3 patients cervical lymph node metastases developed, one patient with high grade transformed MASC died with multiple distant bone metastases, and local recurrence was observed in three patients.

CONCLUSION

Our clinicopathological data are in keeping with previous studies; in most cases, MASC is a low-grade malignancy with overall favorable prognosis. In rare cases, however, MASC with high-grade transformation may behave aggressively, and these patients could benefit from targeted biological treatment using tyrosine kinase inhibitors.

Genomic profiling of breast secretory carcinomas reveals distinct genetics from other breast cancers and similarity to mammary analog secretory carcinomas

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