Mammary analogue secretory carcinoma of the parotid gland: A case report

Abstract Mammary analogue secretory carcinoma (MASC) is a recently described neoplasm characterized by the ETV6-NTRK gene translocation. It is named as such due to its morphologic, genetic and immunohistochemical similarity to secretory carcinoma of the breast. Prior to its description as a distinctive salivary gland neoplasm, MASC was classified as a ‘zymogen-poor' acinic cell carcinoma (AciCC) given their overlapping histological features – therefore AciCC and adenoma not otherwise specified, among other primary salivary gland tumors, are the main differentials for MASC. Here we report a case of MASC in an 87-year old Caucasian lady who presented with a slow growing, painless right mandibular lump who underwent right parotidectomy and neck dissection. Upon pathological analysis of the tumor specimen, many of the classical histopathologic features of MASC are present in this case, emphasizing the importance of molecular screening of salivary gland tumors for ETV6-NTRK3 translocation. Over 100 cases of MASC have been described in the literature, and it is known to be a mostly non-aggressive tumor with good prognosis. MASC commonly occurs in the parotid gland, with a slight preponderance to males. While MASC has been extensively discussed in pathologic literature, clinical information in otolaryngology literature has been scarce. Future research should aim to elucidate its clinical behaviour, disease progression and prognosis to formulate guidelines for the appropriate treatment of this neoplasm.