[Carcinoma in pre-existing Warthin tumors (cystadenolymphoma) of the parotid gland. Classification, pathogenesis and differential diagnosis].

Malignant transformation of pre-existing Warthin tumours of the parotid gland in carcinomas is very rare compared with the development of carcinomas in pre-existing pleomorphic adenomas. Five cases examined in the Salivary Gland Register of Hamburg 1965-1996 were classified in 2 cases as mucoepidermoid carcinoma and in each of one case as oncocytic carcinoma, squamous cell carcinoma and acinic cell carcinoma. In the pathogenesis the benign oncocytic epithelial formations at the surface of the cystic spaces are restricted by malignant neoplastic epithelial cells in the course of which transitions of squamous cell metaplasia or goblet cell metaplasia can be observed. In the further course an infiltrating spread of the carcinoma takes place into the lymphoid stromal component of the Warthin tumour, sometimes also an infiltration of the surrounding tissue und rarely to cervical lymph node metastases. The own findings are analysed concerning the classification of the carcinomas and the differential diagnosis under consideration of the until now reported cases of the literature.