'Benign' pleomorphic adenoma of the parotid

A personal series of 141 surgically treated parotid tumours is reviewed. Of 112 parotid tumours in which a diagnosis of 'benign' pleomorphic adenoma or other benign tumour was made, 8% proved to be malignant on histological examination. Three patients were thought to demonstrate malignant change in long standing 'benign' parotid tumours. It is concluded that in otherwise healthy patients, discrete, mobile parotid tumours should be removed without undue delay because of the risk of misdiagnosis and the chance of late development of malignancy in pleomorphic adenomata. Malignant tumours simulate benign tumours often enough to warrant treating all as potentially malignant.