Mammary Analog Secretory Carcinoma With ETV6 Rearrangement Arising in the Conjunctiva and Eyelid.

Mammary analog secretory carcinoma (MASC) of salivary gland is a recently described neoplasm that morphologically and immunohistochemically resembles secretory carcinoma of the breast. Genetically, both of them harbor ETV-6-NTRK-3 fusion rearrangement. One case of primary MASCs arising from the eyelid is reported. The patient was a 52-year-old man. Microscopically, the tumor exhibited nodular aggregation of solid, tubular, and microcystic/macrocystic structures. Characteristic "colloid-like" eosinophilic secretory material was present within intraluminal spaces. Immunohistochemically, the tumor cells were positive for mammaglobin, S-100, STAT5a, vimentin, GCDFP-15, AE1/AE3, EMA, and CK7 and were negative for DOG-1, CK5/6, and SMA. A dual color break-apart fluorescence in situ hybridization probe identified rearrangement of the ETV6 gene locus on chromosome 12. The patient had no history of breast or salivary gland tumor. The tumor was completely excised, and the patient has no evidence of recurrent disease or metastasis after 1-year follow-up. A diagnosis of primary MASC was rendered. MASC has never been reported occurring in ocular region. This type of secretory carcinoma probably originates from sweat glands or accessory lacrimal glands, Wolfring and Krause. This unique case expands the clinicopathologic landscape of MASCs for better characterization of this rare entity.