Muco-epidermoid carcinoma of the palate.

Abstract

A histological reclassification of 383 tumours in the palate showed a muco-epidermoid carcinoma in 27 cases. The relative incidence of this type of tumour is considerably higher in the minor salivary glands of the palate than in the major salivary glands. The characteristic combination of mucous-secreting cell proliferations and epidermoid differentiation is of diagnostic significance. The tissue structure of origin is present in the terminal portion of the excretory ducts of the salivary glands and it can be concluded that the muco-epidermoid carcinomas develop from the covering epithelium in these ducts. The relatively greater number of such ducts in the palate compared with the major salivary glands might explain the relatively high frequency of mucoepidermoid carcinoma of the palate. A histological grading of the muco-epidermoid carcinomas was based solely upon the cellular structure and the 27 mucoepidermoid carcinomas were divided into two histologically characteristic types of differentiation: one highly and one poorly differentiated. A long-term clinical follow-up study showed that no patient with a highly differentiated muco-epidermoid carcinoma had metastases or died of the tumour disease. The question whether the highly differentiated type of muco-epidermoid carcinoma is to be regarded as benign is discussed. The prognosis of the poorly differentiated muco-epidermoid carcinomas on the other hand was shown to be extremely poor. As the prognosis of highly differentiated muco-epidermoid carcinoma is so different from that of the poorly differentiated type and from that of all other malignant tumours, a histological distinction of the highly differentiated muco-epidermoid carcinoma is very important.