Mucoepidermoid carcinoma arising in a lymphoepithelial cyst--report of a case and review of the literature on branchiogenic carcinoma.

A 59-year-old Japanese man who had recently noticed a gradual enlargement in a nodule located in the left anterior part of his neck was admitted for surgical treatment. The histopathological features of the resected tumor were consistent with a typical lymphoepithelial cyst, however, the inner surface epithelium of the cyst showed histological transition to mucoepidermoid carcinoma, which was partially invading the cyst wall. Despite clinical efforts in a systemic search, no primary lesions which could have metastasized were found. The patient hasn't shown any evidence of recurrence since his tumor resection over 2 years ago. Besides this rare case report, a review of the English literature reveals 22 cases of possible branchiogenic carcinoma over the last 10 years, including 21 cases whose histological features were of squamous cell carcinoma and 1 whose histological features revealed mucoepidermoid carcinoma. The present case is thus only the second proven case of low-grade mucoepidermoid carcinoma arising within a branchiogenic cyst.