A Systematic Review Including an Additional Pediatric Case Report: Pediatric Cases of Mammary Analogue Secretory Carcinoma

Importance Mammary Analogue Secretory Carcinoma (MASC) is a newly characterized salivary gland carcinoma resembling secretory carcinoma of the breast. Prior to being described, MASC was most commonly misdiagnosed as Acinic Cell Carcinoma. Though MASC is predominantly an adult neoplasm, cases have been reported in the pediatric population. Reporting and summarizing of known cases is imperative to understand the prognosis and clinical behavior of MASC. Objective (1) Report a rare case of pediatric MASC. (2) Review and consolidate the existing literature on MASC in the pediatric population. Evidence review Web of Science, Medline, EMBASE, and The Cochrane Library were searched for studies that included pediatric cases of MASC. Data on clinical presentation, diagnosis and management, and pathology were collected from all pediatric cases. Findings Case Report 14 year old with left-sided parotid mass diagnosed as MASC based on histology and immunohistochemistry. He was managed surgically with left superficial parotidectomy with selective neck dissection. Literature review The majority of MASC cases have been identified via retrospective reclassification of previously misclassified salivary gland tumors. Of all the pediatric cases (N=11) of MASC, the female-to-male ratio is 1:1.2 with an age range of 10-17 years old. The most common clinical presentation was a slowly growing, fixed, and painless mass of the parotid gland, often detected incidentally on physical examination. Common pathological features include eosinophilic vacuolated cytoplasm within cystic, tubular, and/or papillary architecture. Immunohistochemistry showed positivity for S100, mammaglobin, cytokeratin 19, and vimentin. The diagnosis was confirmed by the detection of the characteristic ETV6-NTRK6 fusion gene via fluorescent in-situ hybridization (FISH). Only 4 cases discussed treatment. Each of these underwent successful surgical resection alone with or without lymph node dissection. Conclusions and relevance Since the first case of MASC in the pediatric population was described in 2011, only 12 cases, including this one, have been described in the literature. With this paucity of information, much remains unknown regarding this new pathologic diagnosis. The collection of clinical outcomes data of children with MASC is needed to better understand the behavior of this malignancy as well as determine optimal treatment regimens