Myoepithelial and epithelial-myoepithelial clinically advanced and metastatic carcinomas of salivary gland: A comparative comprehensive genomic profiling study.

Myoepithelial carcinoma (MECA) and Epithelial-myoepithelial carcinomas (EMC) are rare salivary gland carcinomas (SGCA) that may arise de novo or in the background of a prior pleomorphic adenoma (carcinoma ex pleomorphic adenoma CAEXPLA). Despite being clinically distinct entities, MECA and EMC share morphologic similarities which can make them difficult to distinguish on histologic examination. Further, there is a currently an evolving understanding of the characteristic genomic and immunohistochemical biomarkers for these tumors. In this study, we characterize the genomic profiles of a relatively large cohort of clinically advanced MECA (n = 52) and EMC (n = 26) cohorts. Both tumor types demonstrated single copy number changes, short variant mutations, and gene rearrangements. The most common alterations in MECA were in CDKN2A and CDKN2B. In EMC, HRAS mutations were the most common alteration, while both PIK3CA and MDM2 mutations were also common. Although not significantly different, CDKN2A and CDKN2B alterations were more frequent in MECA, while PIK3CA alterations were more frequent in EMC. Overall, EMC and MECA had both overlapping and unique molecular alterations that have potential for targeted therapies.