Altered expression of CA-125 in breast carcinomas

CA-125 is a high molecular weight glycoprotein that is best known as a tumour marker for ovarian carcinoma but has been found to be present on various epithelial surfaces including normal tissues. Elevated serum levels of CA-125 have been described in malignancies other than ovarian carcinoma as well as in inflammatory conditions. The expression of CA-125 was studied in paraffin-embedded tissue from 48 mammary carcinomas and 11 samples of normal mammary gland using two monoclonal antibodies, M2 and M11. CA-125 was detected in all normal tissue samples and 64% of the breast carcinomas. Eight of the thirty CA-125-positive carcinomas reacted with only one of the antibodies, indicating molecular change. In normal mammary tissue, CA-125 was seen on apical surfaces and in ductal contents, whilst the majority of the carcinomas (90%) expressed CA-125 in cytoplasmic granules, often showing membranous staining as well. In 16 samples of lymph node metastases CA-125 expression was similar to that seen in the primary tumour. Elevated serum levels of CA-125 were detected in only 3 out of 41 samples available from this patient group. No significant associations were detected with various clinical parameters. We conclude that CA-125 is normally expressed in the mammary gland and that the expression is frequently altered and sometimes absent in mammary carcinoma, possibly reflecting the loss of cellular polarity. Measuring serum levels of CA-125 is not relevant in breast carcinoma patients since one third of breast carcinomas were CA-125 negative and even patients with strongly CA-125-positive tumors had undetectable CA-125 serum levels.