Sclerosing Mucoepidermoid Carcinoma in the Parotid Gland With CRTC1-MAML2 Fusion: A Case Report.

In this article, we report a case of sclerosing mucoepidermoid carcinoma (MEC) arising in the parotid gland, with CRTC1-MAML2 gene fusion. A 73-year-old woman with a mass in the right parotid region was referred to our hospital. Radiological imaging tests revealed a well-defined mass, measuring 25 mm in diameter, with foci of calcification in the deep lobe of the parotid gland, extending to the parapharyngeal space. Microscopically, the tumor was composed of a proliferation of atypical glandular epithelial cells having intracytoplasmic mucin, squamoid cells, and intermediate cells arranged in nests embedded in a fibrosclerotic stroma, associated with a dense chronic inflammatory infiltrate containing immunoglobulin G4-immunoreactive plasma cells. Reverse transcription-polymerase chain reaction analysis using a formalin-fixed, paraffin-embedded tumor tissue specimen revealed the CRTC1-MAML2 fusion gene transcript. This is the first report of sclerosing MEC with the detection of the MEC-associated fusion gene, reinforcing a common genetic association between MEC and sclerosing MEC.