The ovarian cancer associated antigen CA 125 in patients with pleural effusions.

The concentration of the ovarian cancer associated antigen CA 125 was determined in the pleural fluid of 25 patients with lung cancer and of 40 patients with benign diseases. Paired serum and pleural fluid samples were measured in 21 tumor patients and 34 patients with nonmalignant diseases. Serum CA 125 was elevated (greater than 35 U/ml) in 16 of 25 (64%) patients with carcinoma and 13 of 34 (38%) patients with benign diseases. The CA 125 level in serum was markedly elevated (greater than 200 U/ml) in five of six adenocarcinomas whereas a slightly elevated level was associated with only one of four mesotheliomas and with one of three secondary carcinomas. The pleural fluid concentration of CA 125 was higher than the serum value in 90% of the patients, showing a median ratio of 4.9, respectively. Pleural fluid values higher than 250 U/ml were seen in 18 of 25 (72%) subjects with pleural effusion due to malignancy and in 10 of 40 (25%) patients in the benign group. There were no apparent differences in the pleural fluid CA 125 levels in patients having different types of cancer and different benign diseases.