Glycogen-rich clear cell carcinoma of the breast: a light and electron microscopic study.

A glycogen-rich clear cell carcinoma arose in the breast of a 49-year-old woman. Light microscopic examination of the neoplasm revealed both intraductal papillary growth and stromal invasion. Electron microscopic examination demonstrated neoplastic cells that contained massive quantities of nonmembrane-bound particulate glycogen and that formed numerous acini. Apically, these cells formed microvilli; laterally they formed tight junctions and desmosomes. Morphologic features of this neoplasm are similar to those of the fetal breast and to some other clear cell carcinomas arising elsewhere in the body.