A histochemical and ultrastructural study of human breast carcinomas with a view to their classification by cell of origin.

Abstract We have studied 450 cases of human breast carcinoma at the histochemical and ultrastructural level. The breast biopsies were obtained from Canada, Mexico and Dominican Republic. This study was undertaken to evaluate the prognostic significance of classification of breast tumors, proposed in 1971 by Murad, based on their cell of origin. Under this classification, ATPase positive tumors represent those of myoepithelial origin, while the remainder are designated ductal or ductular based upon defined ultrastructural characteristics. We observed a distribution of tumor types essentially similar to that reported by Murad, and no significant differences were observed between the contributing centers. No correlation was observed between this classification and the histological classification described by Stewart. We found no evidence that ATPase positive tumors were myoepithelial in origin. They showed histochemical similarities to ductal and ductular tumors, and had features indicating their secretory nature. Estrogen receptor levels were measured in 20 cases, and did not reveal any correlation with tumor type. An interesting feature requiring further investigation was the high incidence of endocrine-like secretory granules in all histological types of tumors studied.