**10. Common locations of endometriosis**

Most patients with endometriosis have multiple sites of involvement. Endometriosis is located in uterosacral ligaments (63%), ovaries (56%), ovarian fossae (33%) anterior vesicle pouch (22%) pouch of Douglas (19%), intestines, fallopian tube and uterus (5%) There is variation of the distribution among the various series, depending on the diagnostic criteria used, histological or clinical. When histological criteria are used, the ovaries are the most

of Mullerian differentiation from benign to malignant .Many lesions of secondary Mullerian system are described, which are benign, such as endosapingiosis, endocervicosis, of low grade of malignancy, serous and mucinous and malignant ,described as extraovarian peritoneal serous and mucinous carcinomas. The sub-mesothelial stroma gives rise to peritoneal leiomyomatosis and may undergo decidual reaction .Amongst the lesions of secondary Mullerian system are also classed lesions of the retroperitoneal lymph node such as Mullerian inclusions, leiomyomatosis and decidual reaction. Endometriosis is considered as the main lesion of the secondary Mullerian system (Clement & Young, 2008) It has been postulated that the peritoneum of the lower abdominal cavity retains the ability to differentiate to Mullerian tissues due to the proximity to the coelomic epithelium from which the primary Mullerian system is derived. Lauchlan (1994) proposes that the development of peritoneal Mullerian lesions may be secondary to the proximity of pelvic peritoneum to tubal fibria, and the exposure of the peritoneal surfaces to external agents ,

The secondary Mullerian system consists of the covering mesothelial layer and the submesothelial mesenchyme, on and adjacent to the ovaries, the pelvic peritoneum, the omentum and the retroperitoneal lymph nodes. The most common type of epithelial differentiation is a tubal-like epithelium, with ciliated cells. In the omentum and the ovaries cystic inclusions of tubal type epithelium are often observed intermingled with endometrialtype epithelium. Differentiations to mucinous, transitional and squamous type epithelial lesions, benign and malignant are also described. The sub-mesothelial stroma retains the ability to differentiate towards endometrial stroma and smooth muscle tissue and to

**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.

Most patients with endometriosis have multiple sites of involvement. Endometriosis is located in uterosacral ligaments (63%), ovaries (56%), ovarian fossae (33%) anterior vesicle pouch (22%) pouch of Douglas (19%), intestines, fallopian tube and uterus (5%) There is variation of the distribution among the various series, depending on the diagnostic criteria used, histological or clinical. When histological criteria are used, the ovaries are the most

such as talk, that stimulate the peritoneal Mullerian differentiation.

**8. Histological features of the secondary Mullerian system** 

undergo decidual reaction.

**10. Common locations of endometriosis** 

common site (36%) the fallopian tubes, uterus and cul-de-sac account for 6-14% of biopsies, and the uterosacral ligaments account only for 2% of specimens examined. On a clinical basis, 5-12% of women present extrapelvic endometriosis and in descending order in the sigmoid, the appendix, and omentum, on operative scars and in inguinal region. Rarely endometriosis is observed in distant sites such as lungs, brain, bones and skin (Jenkins et al, 1986).
