Immunohistochemical demonstration of steroid C21 hydroxylase in normal and neoplastic human breasts

Steroid C21 hydroxylase was investigated immunohistochemically with the use of antibody against cytochrome P-450 specific for steroid C21 hydroxylation (P-450C21) in normal and neoplastic human breast tissues. In the histologically normal breast, P-450C21 was exclusively present in secretory tubules and ducts. In mammary dysplasia and fibroadenoma, P-450C21 was intensively stained in epithelial cells. In gynecomastia, P-450C21 was faintly observed in epithelial cells in some cases. In intraductal and invasive ductal carcinoma, P-450C21 was observed in the cells with ductal formation. P-450C21 was not observed in medullary and mucinous carcinoma. In lobular carcinoma, only two cases were positive for P-450C21 of nine cases examined. P-450C21 is considered to be closely related to the ductal differentiation in neoplastic transformation of the breast.