Ultrastructural analysis of apocrine carcinoma of the human breast.

A case report with ultrastructural analysis of an apocrine carcinoma of the breast is presented. The key finding with electron microscopy is numerous large mitochondria with abundant incomplete cristae. The ultrastructure of this tumor is compared to the ultrastructure of apocrine cells in the skin, oncocytes, and apocrine metaplastic cells of the breast. The apocrine carcinoma cells have some of the features of typical metaplastic breast epithelium and some features of oncocytes. Their exact origin remains open to speculation.