Electron microscopy and immunostaining of the normal breast and its benign lesions. A search for neuroendocrine cells.

Specimens from 7 patients with normal breast tissue 26 patients with benign breast lesions (6 fibroadenomas, and 4 intraductal papillomas, 2 mammae lactantes, 10 cases of cystic disease and 4 fibrotic lesions) were studied by immunocytochemistry and electron microscopy. Excretory epithelial cells in 2 of the 4 papillomas were immunostained for NSE. Myoepithelial cells were frequently stained as well. All the breast specimens were nonreactive to the antichromogranin antibody we used. The 2 NSE positive intraductal papillomas were tested for presence of hormone immunoreactivity, but no positively stained cells were observed. No cells with neuroendocrine features were observed by electron microscopy. The present study did not reveal neuroendocrine cells in the normal breast specimens and undisputed proof of neuroendocrine differentiation in benign breast lesions was not established. We conclude that if neuroendocrine cells are present in the normal breast, they are very rare, and probably not the cellular origin of all breast carcinomas with neuroendocrine features.