Ki-67, oestrogen receptor, and progesterone receptor proteins in the human rete ovarii and in endometriosis.

AIM To examine proliferative activity using the Ki-67 protein, oestrogen receptor protein, and progesterone receptor protein expression in the rete ovarii, and to make comparisons with their expression in endometriosis. METHODS Immunohistochemistry was used to study the rete ovarii in 24 cases and endometriosis in seven cases, using antibodies to Ki-67 protein (growth fraction (GF) quantified using a point score method) and oestrogen receptor and progesterone receptor (quantified using the H score method). RESULTS There was no evidence of a significant difference in the Ki-67 protein, oestrogen receptor, and progesterone receptor in the rete ovarii in different phases of the menstrual cycle (proliferative phase: GF = 1.052, oestrogen receptor H score = 13.4, progesterone receptor H score = 15.32; secretory phase: GF = 0.736, oestrogen receptor H score = 7.5, progesterone receptor H score = 1.84). The expression of all three proteins was greater in the foci of endometriosis (GF = 6.99, oestrogen receptor H score = 152.02, progesterone receptor H score = 127.36) than in the rete ovarii (p < 0.0005-0.0008, Mann-Whitney U test). CONCLUSIONS There is a low rate of cellular proliferation in the rete ovarii and this structure shows less responsiveness to hormone stimulation than foci of endometriosis. These differences may provide a useful tool to distinguish the rete ovarii from endometriosis in cases of diagnostic difficulty.