Bilateral mucoepidermoid carcinomas arising in bilateral pre-existing Warthin's tumours of the parotid gland.

A unique case of bilateral mucoepidermoid carcinoma arising in pre-existing bilateral Warthin's tumours of the parotid glands is presented. Reports of carcinomas arising in pre-existing unilateral Warthin's tumours are likewise rare with only 3 cases of concern mucoepidermoid carcinoma. This is the first report of bilateral occurrence of mucoepidermoid carcinoma in Warthin's tumours in the literature. The pathogenesis and differential diagnosis are analysed.