A Rare Case of Primary Intraosseous Mucoepidermoid Carcinoma of the Maxilla Diagnosed by MAML2 FISH Testing After Initial Misdiagnosis

We report a case of primary intraosseous mucoepidermoid carcinoma of the maxilla, an exceedingly rare condition with only nine cases documented in the literature, contributing to a prolonged diagnostic timeline. A 58-year-old woman underwent surgery four years earlier for a left maxillary mass at another hospital, initially diagnosed as a calcifying epithelial odontogenic tumor. Due to residual tumor growth, she was referred to our hospital for a second surgery. Histopathological analysis and <i>MAML2</i> gene fluorescence <i>in situ</i> hybridization (FISH) testing confirmed the diagnosis of mucoepidermoid carcinoma. A retrospective review of the tissue from the initial surgery revealed the same diagnosis. This disease poses diagnostic challenges as imaging and histological findings often resemble benign odontogenic cysts. Accurate diagnosis requires awareness of this condition and the application of definitive diagnostic tools. This case highlights the importance of considering intraosseous mucoepidermoid carcinoma in the differential diagnosis of jawbone lesions and the diagnostic utility of <i>MAML2</i> FISH testing.