Malignant lymphoepithelial lesion.

A case of undifferentiated carcinoma arising from benign lymphoepithelial lesion (BLEL) of the parotid gland was studied by light and electron microscopy. Histopathologically, the carcinoma was composed of pleomorphic anaplastic cells showing an undifferentiated type among abundant lymphoid tissue forming germinal center. Among the prominent lymphoid tissue, epithelial hyperplasia, dysplasia, and squamous metaplasia of the duct epithelium were found. Dysplastic epithelium revealed a transition with carcinomatous component in some areas. On the electron microscopic observation, the tumor cells were poorly differentiated, possessing desmosomes and intracytoplasmic filaments. The patient is alive and well 2 months after resection of the tumor, but has a high titer of serum Epstein-Barr virus capsid antigen in IgG. Eighty five cases of the malignant lymphoepithelial lesion (MLEL) including the present case are summarized.