Tumor-associated antigens in effusions of malignant and benign origin.

We determined the concentration and effusion/serum ratio of mucin-like carcinoma-associated antigen (MCA) in comparison to carcinoembryonic antigen, carbohydrate antigen 19-9, cancer antigen 125, and cancer antigen 15-3 in 80 sera and 99 effusions from 64 patients with histologically confirmed malignancies (4 patients out of this group showed various effusions simultaneously, which were analyzed separately) and 31 patients with various nonneoplastic diseases. Tumor cells were detected by cytological examination in 41 effusions (60.3%) from patients with neoplastic diseases, while in another 27 cases this method failed to demonstrate the malignant origin of the effusion. Of the cytological "positive" malignant effusions 90% were also correctly identified by an elevated MCA concentration at a cutoff level of 10 U/ml, whereas only one effusion of benign origin (3%) showed a slightly elevated MCA concentration of 10.5 U/ml. In 33% of cytologically "negative" effusions of patients with neoplastic diseases, the MCA concentration was also elevated, with a maximum of 453 U/ml. Increased MCA levels in cytologically confirmed malignant effusions were not restricted to metastatic breast cancer. All 17 cytologically "positive" "non-breast cancer" effusions were correctly identified by their MCA concentrations. None of the other tumor markers reached this high sensitivity at the same level of specificity. The ratio of effusion/serum concentration of all tumor markers as well as the concentration of cancer antigen 125 in effusions was of little diagnostic value. Our results indicate that the MCA concentration in an effusion correlates very closely with its malignant origin and is superior to all the other antigens tested.(ABSTRACT TRUNCATED AT 250 WORDS)