[1299] Mammary Analogue Secretory Carcinoma (MASC) of the Salivary Gland: Revisiting Our Acinic Cell and Poorly Differentiated Carcinomas Using Immunohistochemistry and FISH Studies

Andre Pinto, Vania Nose, Yao-Shan Fan, Carmen Gomez-Fernandez. University of Miami, Miami, FL

Background: Mammary analogue secretory carcinoma (MASC) is a recently described entity with unique morphological, clinical and genetic characteristics. These tumors were previously diagnosed as acinic cell carcinomas (ACC) or poorly differentiated carcinomas, among others. A few institutions have reviewed these cases and reported their experience.
Design: All cases of ACC and poorly differentiated carcinomas of the salivary glands in a ten year period were reviewed. There were a total of 27 cases, including 11 cases of acinic cell carcinomas and 16 cases of poorly differentiated carcinomas. The hematoxylin and eosin stained slides were reviewed and tumors that morphologically fit in this new category- MASC- according to the recent literature were selected. Those features included epithelial cells with abundant vacuolated cytoplasm, minimal nuclear pleomorphism, papillary and microcystic architecture with cellular hobnailing and eosinophilic secretions. This process narrowed down the initial number to 12 cases (7 ACC and 5 poorly differentiated adenocarcinomas) on which S-100, mammoglobin (MMG) and DOG1 immunostains were performed. The cases that were immunoreactive for S-100 and nonreactive for DOG-1 were then submitted for FISH analysis for the characteristic t(12;15)(p13;q25) with ETV6-NTRK3 fusion.
Results: Six (6) cases demonstrated positivity for S-100 protein and negativity for DOG1 by immunohistochemistry. FISH studies confirmed ETV6-NTRK3 rearrangement in three (3) cases, initially diagnosed as ACCs. The three cases stained positive for MMG by immunohistochemistry. One (1) additional case had amplification of the ETV6 gene, and 1 case had deletion of ETV6. The remaining case had no cytogenetic abnormalities detected. Among the three tumors with t(12;15)(p13;q25), two patients were male (2/3). The two cases on which ETV6 gene was amplified (1) and deleted (1) were also from male patients.
Conclusions: MASC is a new diagnostic entity that should be in the differential diagnosis of salivary gland tumors that mimic ACC. They differ from conventional ACC morphologically, immunohistochemically and molecularly. S-100 protein is positive, as opposed to the majority of ACC. They predominantly affect male patients. Positivity for MMG and S-100 and negativity for DOG1 are useful screening tools prior to further confirmatory FISH studies. The novel finding of deletion and amplification of ETV6 in MASC, with absent ETV6-NTRK3 rearrangement, may indicate an additional pathogenetic pathway of this neoplasm.
Category: Head & Neck

Tuesday, March 5, 2013 9:30 AM

Poster Session III # 147, Tuesday Morning

 

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