Cell proliferation is increased in the endometrium of women with endometriosis.

OBJECTIVE: To compare the proliferation of endothelial, epithelial, and stromal cells in the endometrium of women with endometriosis and normal controls.
DESIGN: Proliferating cells were identified using the monoclonal antibody antiproliferating cell nuclear antigen. A second antibody (CD34) was used to identify endothelial cells (ECs).
SETTING: University Department of Obstetrics and Gynaecology. PATIENTS: Women with laparoscopically proven endometriosis, n = 30. Controls were women with a normal pelvis at laparoscopy performed for tubal sterilization or for infertility due to a male factor, n = 27. MAIN OUTCOME MEASURES: Endothelial cells: proliferative index. Epithelial and stromal cells: semi-quantitative immunostaining score.
RESULTS: The mean EC proliferative index was significantly greater in those with endometriosis compared with controls. This difference was most marked during the proliferative phase of the menstrual cycle. Proliferative phase epithelial and stromal cells demonstrated significantly higher immunostaining scores in endometriosis patients than in controls.
CONCLUSIONS: We have demonstrated increased numbers of proliferating ECs as well as epithelial and stromal cells in proliferative phase endometrium of women with endometriosis. This suggests that the endometrium of these women might have an enhanced ability to implant and survive in ectopic locations.