Lobular carcinoma in situ. Some ultrastructural observations

Bilateral, multifocal areas of lobular carcinoma in situ in the breast of two women were examined by electron and light microscopy. A striking dilatation of the Golgi apparatus was observed in the hyperplastic epithelial tumor cells which contained granular material of varying electron density within the cisternae, suggesting a secretory and/or concentrating activity. Abundant tumor cells filled the dilated mammary ductules leaving small, irregular luminal renants and occasional “pseudo-intracytoplasmic” lumens. The tumor cells related to each other by an intricate system of microvilli and well-defined desmosomes; however, large intercellular cisternae were observed in some areas as if the cells had lost cohesiveness. Well-defined myoepithelial cells at the periphery of the dilated ductules revealed vacuolation, and fragmentation of the cytoplasm. It is possible that lobular carcinoma in situ is mostly an epithelial lesion; the myoepithelial cells are not participating in the neoplastic process and they seem to be crowded and compressed by the proliferating tumor cells against the basement lamina.