Adenoid cystic carcinoma of the breast: prevalence, diagnostic criteria, and histogenesis

Abstract

Adenoid cystic carcinoma (adenocystic carcinoma, cylindroma, basaloid carcinoma) is best known as a tumor of salivary glands though it infrequently also occurs at other sites in the body, e.g. the tracheo bronchial tree, nasopharynx, maxillary sinus, uterine cervix, and the skin. 3 Cases of adenoid cystic carcinoma have been identified in a 10 yr review of 2,686 cases of breast carcinoma. The criteria necessary for diagnosis are reviewed with particular reference to cribriform intraduct carcinoma and adenocarcinoma of the breast with a small, dark, 'basaloid' cell pattern. The most important single diagnostic criterion of adenoid cystic carcinoma is a biphasic cellular pattern which may be aided by the demonstration of 2 types of mucin - stromal acid mucopolysaccharide and ductal neutral mucopolysaccharide. This tumor most frequently presents as a painful or tender mass near the areola, and it carries a uniquely favorable prognosis when compared with similar tumors elsewhere in the body. Actomyosin has been demonstrated in all 3 tumors by an immunofluorescent method, and this supports a predominantly myoepithelial origin. Yet, the identity of 'basaloid' tumors remains in doubt. Tumors with such appearances should be regarded as variants of 'ordinary' adenocarcinoma unless evidence to support a myoepithelial origin can be found. The cytological features suggest that it originates from myoepithelial cells, but it also has a secretory, ductal element, and electron microscopy studies have shown evidence of both types of cell. The interpretation of ultrastructural appearances has given rise to some controversy between those who favor a predominantly ductal epithelial or a predominantly myoepithelial origin. Filamentous material resembling myofibrils has also been demonstrated with phosphotungstic acid hematoxylin, but this could not be confirmed.