Epidermoid carcinoma arising in Warthin's tumour: a case study.

We present a case of epidermoid carcinoma arising in Warthin's tumour of parotid gland in an 80-year-old woman. Light microscopy revealed small foci typical of benign Warthin's tumour with transition to epidermoid carcinoma. Immunohistochemical and ultrastructural observations confirmed the epidermoid features of the malignant cells. The differential diagnosis of a metastasis from an epidermoid carcinoma to the stroma of Warthin's tumour and also of the so-called metaplastic variant of Warthin's tumour is discussed.