Phenotypic expression of immune secretory function in focal pregnancy-like change of the human breast.

Fibrocystic disease of the breast in middle-aged women characteristically shows focal epithelial lesions of a very varied nature. The functional immunohistochemical changes in such lesions have been little studied. Focal Pregnancy-like Change in the breast has a striking morphological similarity to the secretory breast lobules in pregnancy and in lactation. We show that the epithelial cells in all the lesions of Focal Pregnancy-like Change studied simultaneously express secretory component, Ig A and J chain in their cytoplasm. Additionally these epithelial cells, unlike those in resting breast lobules, contain lysozyme and lactoferrin. All these phenotypic immunohistochemical changes in Focal Pregnancy-like Change resemble the breast lobules of late pregnancy and lactation. Possibly, the very focality of Focal Pregnancy-like Change reflects a peculiar and local sensitivity of 'resting' breast lobules to unidentified hormonal stimulation.