einstein (São Paulo). 08/Apr/2026;24:eAO1591.
Preliminary diagnostic criteria for distinguishing metaplastic Warthin tumors from mucoepidermoid carcinomas rich in lymphoid stroma
DOI: 10.31744/einstein_journal/2026AO1591
Highlights
■ Immunohistochemistry distinguishes Warthin-like mucoepidermoid carcinoma from metaplastic Warthin tumor.
■ CK7, mitochondrial patterns, and double-layer epithelium suggest metaplastic Warthin tumor.
■ Basal CK14, CK5/6, and p63 distinguish metaplastic Warthin tumor from Warthin-like mucoepidermoid carcinoma.
ABSTRACT
Objective:
This study aimed to analyze the clinicopathological and immunohistochemical profiles of unconventional Warthin tumors and mucoepidermoid carcinomas.
Methods:
Eleven low-grade salivary gland tumors with Warthin-like features were analyzed. Group A (n=6) showed a double-layered oncocytic epithelium in less than 50% of the epithelial cells, whereas Group B (n=5) lacked this feature. Additionally, five conventional Warthin tumors and ten conventional mucoepidermoid carcinomas were analyzed as reference groups. Immunohistochemical staining was performed for cytokeratins (types 5/6, 7, and 14), p63, mitochondrial antigens, and Ki-67. Expression patterns were compared between groups.
Results:
Group A exhibited an oncocytic epithelium arranged in a double-layered pattern, with mitochondrial antigens strongly staining the luminal oncocytic cells. Cytokeratin 7 expression in Warthin tumors was predominantly luminal. In contrast, Group B showed glandular and cystic structures with diffuse mitochondrial antigen and cytokeratin 7 positivity. Immunohistochemical analysis revealed significant differences, with Warthin tumors showing distinct double-layered epithelial structures, and mucoepidermoid carcinomas displaying diffuse staining patterns.
Conclusion:
Distinct immunohistochemical profiles, including mitochondrial antigen and cytokeratin 7 expression, along with morphological differences, support the classification of Group A as metaplastic Warthin tumors and Group B as Warthin-like variants of mucoepidermoid carcinoma. These findings highlight the importance of molecular and immunohistochemical analyses for accurate classification of these tumors.
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