Ultrastructure of tubular carcinoma of the breast

Abstract

Two cases of infiltrating tubular carcinoma of the breast were studied by electron microscopy. Our findings indicate that these tumors are composed of duct (or ductular) epithelial cells exhibiting varying degrees of differentiation. In the well-differentiated tumor, the cells very closely resembled those of the normal duct with respect to fine structure and polarity. Differences include the more extensive formation of apical and basal cytoplasmic protrusions, and increased numbers of intracellular lumens and tonofilaments. Solid nests of tumor cells were also seen. Myoepithelial or myoepithelial-like cells were rarely observed, and basement membrane investment of the tubules was incomplete or totally lacking. In the less-differentiated tumor, the cells were more pleomorphic and showed loss of polarity, but still formed lumens. The epithelial cells comprising tubular carcinoma were also quite similar in fine structure to the cells found in some reported cases of well-differentiated intraductal and infiltrating duct carcinomas.