AbstractMyoepithelial carcinoma (MECA) is an aggressive type of salivary gland cancer with largely unknown molecular features. MECA may arise de novo or result from oncogenic transformation of a pre-existing pleomorphic adenoma (MECA ex-PA). We comprehensively analyzed the molecular alterations in MECA with integrated genomic analyses. We identified a low mutational load (0.5/MB), but a high prevalence of fusion oncogenes (28/40 tumors; 70%). We foundFGFR1-PLAG1in 7 (18%) cases, and the novelTGFBR3-PLAG1fusion in 6 (15%) cases.TGFBR3-PLAG1was specific for MECA de novo tumors or the malignant component of MECA ex-PA, was absent in 723 other salivary gland tumors, and promoted a tumorigenic phenotype in vitro. We discovered other novelPLAG1fusions, includingND4-PLAG1,which is an oncogenic fusion between mitochondrial and nuclear DNA. One tumor harbored anMSN-ALKfusion, which was tumorigenic in vitro, and targetable with ALK inhibitors. Certain gene fusions were predicted to result in neoantigens with high MHC binding affinity. A high number of copy number alterations was associated with poorer prognosis. Our findings indicate that MECA is a fusion-driven disease, nominateTGFBR3-PLAG1as a hallmark of MECA, and provide a framework for future steps of diagnostic and therapeutic research in this lethal cancer.
De novo myoepithelial carcinoma with multiple metastases arising from a submandibular salivary gland: A case report
