CA 125 in serum, peritoneal fluid, active lesions, and endometrium of patients with endometriosis.

Ca 125 levels in serum and peritoneal fluid were measured in 39 patients with endometriosis and 18 patients with normal pelvic anatomy at laparoscopy, and the presence of this antigen in endometriotic tissue and endometrial mucosa was also investigated. Serum CA 125 concentrations were elevated in patients with Stage III or IV endometriosis compared with control subjects (32.9 +/- 11.2 versus 16.4 +/- 8.9 U/ml, means +/- SD; p less than 0.001). CA 125 values were greater than 35 U/ml in 36.8% of women with Stage III or IV endometriosis and in none of the control subjects. No significant differences in CA 125 levels in peritoneal fluid were found between patients with endometriosis and control subjects. The immunohistochemical studies found CA 125 in 10% of the endometriotic lesions and 37.5% of the endometrial samples of patients with endometriosis and in 33.3% of the endometrial samples of control subjects.