A challenging diagnosis of Mammary analogue secretory carcinoma (MASC) on fine needle aspiration cytology & cell block: A Cytopathologist perspective.

Mammary analogue secretory carcinoma (MASC) is a recently described salivary gland carcinoma that resembles the secretory carcinoma of the breast and is characterized by t (12;15) (q13;q25) translocation, which results in an ETV6-NTRK3 gene fusion product. On cytomorphology, it is characterized by papillary fragments, clusters, and singly dispersed tumor cells. These tumor cells are large and have abundant vacuolated cytoplasm. Acinic cell carcinoma of the salivary gland is the most common differential diagnosis of MASC. Other differentials include mucoepidermoid carcinoma (MEC), salivary duct carcinoma (SDCA), Pleomorphic adenoma (PA), and oncocytic salivary gland neoplasms. Immunohistochemistry (IHC) and morphology are critical in establishing a correct diagnosis. We present a case of a 46-year-old male patient diagnosed as MASC of the parotid gland on fine-needle aspiration cytology (FNAC) & cell block.