Adenoid cystic carcinoma of minor salivary glands. Analysis of 86 cases

Summary

819 salivary gland tumors in surgical pathology files over a 25-year period were reviewed. Among 117 adenoid cystic carcinomas, 86 were located in minor salivary glands and were selected for a clinico-pathological analysis. Complementary histoenzymological investigations and electron microscopic study were performed on specimens from 7 and 13 patients respectively.

Adenoid cystic carcinoma occured in older patients (mean age of 54 years) than the other salivary neoplasms. The sex ratio was 1/1. The tumor was located more often in the palate and, to a lesser degree in the buccal floor, tongue or gums.

Histologically, epithelial nests contained characteristic cyst-like spaces (cylinders) and 3 varieties of such cylinders were described (mucoid, mucohyalin and hyalin). According to the predominant pattern, 3 types of tumors were shown: basaloïd, cribriform and trabecular. A comparison between histological results and clinical behaviour, available in 67 patients, demonstrated positive correlations. The basaloïd form had always a poor prognosis (numerous early recurrences and metastases, frequent lethal evolution). The cribriform type had an intermediate prognosis, better than basaloïd type and less good than trabecular group (100% of patients still alive at 8 years).

Histoenzymological studies revealed high level of acid phosphatase, alkaline phosphatase and leucine aminopeptidase activities round cylindromatous cavities. On the other hand, high oxidative enzyme activities were evenly distributed in all cell types.

Ultrastructural findings emphasized the immature characters of epithelial tumor cells. These cells contained numerous ribosomes, but few other organelles. Some more differentiated glandular or epidermoid cells were scattered in neoplastic islands. Rare myoepithelial cells lay in periphery of lobules. Cylinder-like spaces were filled with replicated basal lamellae, mucopolysaccharidic granules and fibrillar structures (microfibrils and periodic collagen fibrils).

In the light of these results the histogenesis of this neoplasm was discussed. Like the pleomorphic adenoma, adenoid cystic carcinoma was thought to arise from intercalated ducts. Unable to acquire any high degree of differentiation, this blastomatous tumor had a cellular component almost similar to that shown in intermediate stage of salivary gland embryogenesis.