Elevated serum concentrations of CA-125 in patients with advanced endometriosis.

CA-125 is a high-molecular-weight glycoprotein that is expressed on the cell surface of some derivatives of embryonic coelomic epithelium. Based on results of an immunoradiometric assay developed to detect CA-125 in peripheral blood, 82% of patients with ovarian cancer and less than 1% of apparently healthy controls have elevated peripheral blood levels of CA-125. Because endometriotic lesions are likely to be derivatives of embryonic coelomic epithelium, the authors investigated serum CA-125 levels in patients with endometriosis. Preoperative serum CA-125 concentrations were measured in 147 patients undergoing diagnostic laparoscopy or laparotomy. Serum CA-125 concentrations were elevated in patients with stage III or IV endometriosis, compared with controls with negative diagnostic laparoscopies (66.5 +/- 14.5 versus 8.20 +/- 0.59 U/ml, mean +/- standard error of the mean; P less than 0.001). Fifty-four percent of patients with stage III or IV endometriosis and 0% of the controls had CA-125 levels greater than 35 U/ml. Occasional patients with stage II endometriosis (13%), leiomyomata uteri (14%), and chronic pelvic inflammatory disease (5%) also had serum CA-125 concentrations greater than 35 U/ml. Immunocytochemical techniques demonstrated the presence of CA-125 on the cell surface of endometriotic lesions.