Morphological Investigation of Human Breast Cancer2

Abstract

Twenty-two human breast cancers and two benign breast tumors were studied in the electron microscope. Human breast tumors were found to retain certain characteristics of their tissue of origin. There was some ductal differentiation in all these tumors. Unlike normal epithelial cells of the mammary gland, tumor cells frequently showed intracytoplasmic ductules and numerous cytoplasmic microfibrils identified as tonofibrils. These two cytological features were considered pathognomonic for cancer cells. The significance and nature of the nuclear “inclusions” and of some cytoplasmic structures described are unknown. No structures resembling any known infectious or oncogenic viruses were observed in the human breast material examined.