Apocrine differentiation in human mammary carcinoma

Abstract

Six invasive carcinomas that contained apocrine differentiation as the primary morphologic pattern were selected from 1500 prospectively examined breast carcinomas (0.4%). While apocrine features were seen in many breast tumors, these 6 cases were identified by uniformly fine granular, pale, eosinophilic cytoplasm with apical cytoplasmic projections similar to that seen in apocrine metaplasia. In each example, ultrastructural analysis revealed the presence of numerous 400-600 nm membrane vesicles with dense homogeneous osmophilic cores. These granules clustered toward the apex of the cytoplasm in the majority of the epithelial cells. All 6 tumors were deficient in high-affinity, low-capacity 8S estrogen and progesterone proteins, while a high-capacity, low-affinity, nonsaturable 4S progesterone-estrogen binding protein was observed. Cortisol did not bind to this protein. The ultrastructure of apocrine carcinoma as a variant of human mammary carcinoma was characterized.