It is currently thought that most clear cell and endometrioid carcinomas arise from ovarian endometriosis. We recently suggested that, besides their origin in the ovary, reduction of CDC42 messenger RNA (a member of the RHO GTPase family) may contribute to explain why clear cell carcinomas are not uncommonly found limited to the ovary (stage I). On the other hand, little is known about the expression of CDC42 in ovarian endometriosis with and without carcinoma. Twenty-two endometriotic cysts not associated with carcinoma, 19 endometriotic cysts associated with carcinoma (contiguous endometriosis), as well as the 19 corresponding tumors (11 clear cell, 4 endometrioid, and 4 mixed-clear cell and endometrioid-carcinomas) were investigated. We analyzed CDC42 expression both by real-time polymerase chain reaction and immunohistochemistry. Endometriotic cysts not associated with carcinoma showed higher expression of CDC42 messenger RNA than cysts associated with carcinoma (P = .002). Immunohistochemically, CDC42 was exclusively expressed by macrophages. CDC42-positive macrophages were present in most of the endometriotic cysts not associated with carcinoma (11/19, or 58%). In contrast, only 5 endometriotic cysts containing carcinoma (contiguous endometriosis) (5/18, or 28%) and 1 ovarian carcinoma arising from endometriosis (1/18, or 5%) had CDC42-positive macrophages (58% versus 28%, P = .065; 28% versus 5%, P = .046). Our results raise the possibility that CDC42-positive macrophages may prevent the development of endometrioid and clear cell carcinomas.
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