Immunohistochemical detection of the estrogen-regulated 52,000 mol wt protein in primary breast cancers but not in normal breast and uterus.

An estrogen regulated glycoprotein of molecular weight 52,000 is released by metastatic human breast cancer cells in culture. In order to detect this protein directly in human tissues, several high affinity monoclonal antibodies were produced against the 52,000 mol wt protein. Frozen sections of human breast cancer samples were stained by the peroxidase-anti-peroxidase method using these antibodies. In 20 of 25 samples, specific immunoperoxidase staining was observed in the cytoplasm of epithelial cells with six monoclonal antibodies to the 52,000 mol wt protein. The 5 samples that were not stained contained no detectable estrogen receptor. Epithelial cells were not stained in 6 normal mammary glands collected during reduction mammoplasties and in 9 normal uteri, whether tissues were collected during the follicular or luteal phase. The demonstration that the 52,000 mol wt estrogen regulated protein is present in the cytoplasm of some primary breast cancers but absent in normal mammary tissue and uterus indicates its possible use as a tumor marker.