[1270] Utility of Mammaglobin Immunostaining in the Diagnosis of Mammary Analogue Secretory Carcinoma of the Salivary Glands

Justin A Bishop, Raluca Yonescu, Denise Batista, William H Westra. Johns Hopkins Hospital, Baltimore, MD

Background: Mammary analogue secretory carcinoma (MASC) is a recently described salivary gland neoplasm that is defined by ETV6-NTRK3 gene fusion. The morphologic features of MASC have been previously described, but they are not entirely specific and overlap with other salivary gland tumors. As a result, diagnosing MASC currently rests on documenting ETV6 rearrangement, but performing the required molecular tests is not feasible for most surgical pathology laboratories. Mammaglobin immunohistochemistry, on the other hand, is widely available, and has been reported to be frequently positive in MASC. This antibody has yet to be tested against molecular methods on a large number of diverse salivary gland tumors.
Design: Fifteen MASCs confirmed by ETV6 FISH were tested with mammaglobin immunohistochemistry (clone 304-1A5; DAKO GenPoint, Carpinteria, CA; 1:200 dilution). In addition, tissue microarrays containing a diverse collection of FISH-proven ETV6 wild-type salivary gland neoplasms (44 adenoid cystic carcinomas, 33 pleomorphic adenomas, 18 mucoepidermoid carcinomas, 8 acinic cell carcinomas, 4 adenocarcinomas not otherwise specified, 3 polymorphous low grade adenocarcinomas, and 2 salivary duct carcinomas) were also tested.
Results: All 15 (100%) MASCs were strongly and diffusely mammaglobin-positive. However, mammaglobin staining was also seen in 2/3 (67%) polymorphous low grade adenocarcinomas, 2/2 (100%) salivary duct carcinomas, 1/8 (13%) acinic cell carcinomas, 2/18 (11%) mucoepidermoid carcinomas, and 2/33 (6%) pleomorphic adenomas. Overall, mammaglobin immunostaining was 100% sensitive and 92% specific for MASC.
Conclusions: Mammaglobin immunostaining is highly sensitive for the diagnosis of MASC. However, caution must be exercised in using mammaglobin immunohistochemistry in place of ETV6 molecular testing since other salivary gland tumors may be positive. Accordingly, mammaglobin staining should be carefully interpreted in the context of a tumor's histologic features.
Category: Head & Neck

Tuesday, March 5, 2013 9:30 AM

Poster Session III # 146, Tuesday Morning


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