Characterizing Warthin-Like Mucoepidermoid Carcinoma: Clinicopathologic Features and MAML2 Rearrangements in 14 Latin American Cases

PURPOSE: Warthin-like mucoepidermoid carcinoma (WL-MEC) is a low-grade variant of mucoepidermoid carcinoma (MEC), characterized by a multicystic growth pattern and dense lymphoid stroma, histologically mimicking Warthin tumor (WT). Few cases have been reported, limiting understanding of this variant. We aimed to provide a comprehensive clinical, histopathologic, and molecular analysis of new WL-MEC cases. METHODS AND RESULTS: Fourteen WL-MEC cases from Brazil, Guatemala, and Mexico were analyzed. Clinicopathologic features (patient demographics, tumor location, AFIP grading, follow-up, recurrence), histological characteristics (architectural patterns, inflammatory infiltrate, epithelial components, invasion), and immunohistochemical profiles (CK5/6, p63, p40, CK7, CK14, Ki67, HER2) were assessed. MAML2 generearrangements and HER2 amplification were evaluated by fluorescence in situ hybridization (FISH). All 14 cases showed MAML2 rearrangement (100%), confirming the diagnosis, while HER2 amplification was absent in all 9 cases tested. CONCLUSIONS: This study provides new insights into the clinicopathological and molecular features of WL-MEC, confirming its typical presentation (parotid gland, middle-aged females), low-grade behavior, and favorable prognosis after surgical excision. Detection of MAML2 rearrangement is a valuable diagnostic tool for distinguishing WL-MEC from WT.