Submandibular gland tumors - Local clinical implications of their low malignancy rates

Background: According to previous reports, the malignancy rate of submandibular gland tumors is about 35%-50%. However, the rate has seemed much lower in Taiwan. Further studies of the epidemiology and the possible etiology of this disease are needed. Method: We did a retrospective study of 126 patients with submandibular gland tumors who had undergone operations at our hospital from January 1986 to June 1997. Of these, 71 were women and 55 men, with ages ranging from 12 years old to 74 years old. The histological findings, age, sex ratio and prognosis were all analysed. Results: Of the 126 submandibular gland tumors, 106 were benign and 20 were malignant. The malignancy rate was only 15.9%. The average age of persons with benign tumors was 36.9 years and the average age of those with malignancy was 51.2 years. The male to female ratio was 1:1.52 for benign tumors and 1:0.53 for malignant tumors. Of the 106 benign tumors, 103 were pleomorphic adenomas. Of the 20 malignant tumors, 10 were adenoid cystic carcinomas. 6 were malignant mixed tumors and 2 were mucoepidermoid carcinomas. No recurrence was found in any benign tumors postoperatively. The 2-year survival rate for persons with malignant tumors were 72.2% and the 5-year survival rate was 52.9%. Conclusion: The malignancy rate of the 126 submandibular gland tumors was only 15.9%, much lower than the rates in previous reports. Further study is suggested about the correlations between the malignancy rates and human races, dietary, etc.