Immunohistochemistry of a component protein of the breast cystic disease fluid with mol. wt 15,000.

A specific protein from the liquid of a mammary cyst with a molecular weight of 15,000 (GCDFP 15) was studied in normal and pathological mammary tissue using an immunohistochemical method (peroxidase-anti-peroxidase complex). An immunoreactivity of the GCDFP type was found in normal idrosadenoid glands having an apocrine secretion. Histologically normal mammary tissue was not immunoreactive. In benign breast tissue the GCDFP was found particularly in epithelium undergoing apocrine metaplasia (55/55) and in atypical lobular epithelial hyperplasia (8/10). Of the adenocarcinomas of the breast 136/161 (84%) were immunoreactive, especially lobular carcinoma (13/13). The proportion of tumors with a high percentage of immunoreactive cells (76-100%) was greater for Bloom's grade I (1/29: 34%) than for grade III (10/66: 15%). A significant correlation was found between the percentage of immunoreactive cells and the cytosolic concentration of progesterone receptors. The morphological intracellular identification of GCDFP (due to its greater sensitivity) and its correlation with progesterone receptors allowed a more precise evaluation of the functional state and the hormonal dependency of the breast cells by underlining the heterogeneity of the tumoral cell population.