Pleomorphic Adenoma with Extensive Mucinous Metaplasia Mimicking Mucoepidermoid Carcinoma: A Case Report and Literature Review

Abstract

Pleomorphic adenoma is the most common benign tumor of the salivary glands. Histologically, it is characterized by the presence of both epithelial and mesenchymal elements and may contain various metaplastic changes. This paper reported a case of pleomorphic adenoma with extensive mucinous metaplasia, which is histologically very similar to mucoepi-dermoid carcinoma. Pleomorphic adenoma with extensive mucinous and squamous differentiation may be misdiagnosed as mucoepidermoid carcinoma. Immunohis-tochemistry was ineffective in differential diagnosis, and the diagnosis was confirmed by the absence of mastermind like transcriptional coactivator 2 (MAML2) translocation. The detection of MAML2 translocation can help avoid misdiagnosis of MEC in similar cases. Additionally, the published literature on metaplasia on pleomorphic adenoma was also reviewed and summarized. © 2025 Elsevier B.V., All rights reserved.