Intracytoplasmic lumina in breast carcinoma: a helpful histopathologic feature.

Eelectron microscopy has disclosed the presence of intracytoplasmic lumina within breast cancer cells. These structures can be recognized with the light microscope by their sharp, round outlines and thick walls. Their identification in large numbers may provide additional support for the breast origin of a metastatic tumor. Three illustrative cases in which demonstration of intracytoplasmic lumina was diagnostically helpful are presented.