**9. Elevated serum CA- 125 levels may be expressed in endometriosis**

CA 125 is an antigenic determinant recognized by the monoclonal antibody OC125 against an ovarian cancer cell line. The serum CA125 levels are increased in women with benign conditions such as endometriosis, pelvic inflammatory disease and pregnancy. Ca125 is detected by immunohistochemical methods in fetal coelomic epithelium, fetal Mullerian ducts and Mullerian-derived epithelia in the adult. In the fetus, CA125 is detected in the peritoneum, ovaries and Mullerian ducts after 15 weeks gestation and after the 23rd week it is strongly expressed in endometrium, tubes and cervical tissues.CA125 is considered a differentiation antigen associated with fetal coelomic tissues, derived from embryonic mesoderm Lesions derived from embryonic coelomic tissues either the primary or the secondary Mullerian systems, such as endometriosis, retain the ability to express CA 125.
