Multiple primary tumours of the parotid gland.

The authors reviewed the clinical and histopathological records of 69 cases of multiple primary tumours (MPT) of the parotid gland treated at Peking University School of Stomatology. It accounted for 3.4% of all parotid tumours (2055 patients). Fifty-nine patients were male and 10 were female. The median age was 58 (range 24-80) years. The average time interval between the diagnosis of bilateral parotid tumours was 5 years (range 5 months-15 years). Three clinical types were classified as bilateral parotid tumours (31 cases), unilateral multifocal parotid tumours (29 cases), and the combination of bilateral parotid tumours with unilateral multifocal parotid tumours (9 cases). Histologically, Warthin's tumour was the most common type (60 patients), followed by pleomorphic adenoma (8 cases). Three cases were malignant including adenoid cystic carcinoma, squamous cell carcinoma and mucoepidermoid carcinoma. The histopathologies of tumours were of the same type in 63 patients, and distinctly different in six patients. The tumours were found and diagnosed synchronously in 48 patients, and metachronously in 21 patients. Since some parotid tumours are MPTs, careful preoperative diagnosis is necessary. B-mode ultrasound is the technique of choice for the screening of MPT. Meticulous intraoperative inspection and palpation of the glandular tissues and periglandular lymph nodes are necessary.