Mucoepidermoid carcinoma of the sublingual gland harboring a translocation of the MAML2 gene: A case report

Among tumors of the major salivary glands, tumors in the sublingual gland are rare. Although mucoepidermoid carcinoma (MEC) represents a histological type of salivary gland tumor, it is occasionally difficult to diagnose due to its histological variation. The present study reports a case of MEC harboring a mastermind-like transcriptional coactivator 2 (MAML2) gene translocation in the sublingual gland. A 76-year-old Japanese woman with a mass in the left submandibular region was referred to Kurume University Hospital (Kurume, Japan). Computed tomography scans revealed that the tumor was predominantly located in the sublingual gland, and tumor resection was performed. Histologically, the tumor was composed of cells that exhibited low-grade nuclear atypia and clear and/or granular eosinophilic cytoplasm, and that were proliferating in solid patterns. Periodic acid-Schiff and alcian blue staining revealed a small number of mucinous cells in the tumor. Immunohistochemically, the tumor cells were positive for p40 and p63. Fluorescence in situ hybridization (FISH) analysis revealed a MAML2 gene split. The definitive pathological diagnosis was low-grade MEC, as the case lacked any factors indicative of high-grade malignancy. To the best of our knowledge, this is the first report of MEC in the sublingual gland with MAML2 gene translocation confirmed by FISH.