Clear cell carcinoma arising in extraovarian endometriosis: report of three cases and review of the literature.

The literature on malignancy arising in extraovarian endometriosis comprises only three cases of clear cell carcinoma. We wish to report the clinical features and pathologic findings of an additional three cases. The first concerns a 39-year-old oriental pregnant woman who presented with a large intraluminal obstructing lesion of the sigmoid colon, the second case deals with an abdominal wall mass that appeared in a cesarean section scar of a 45-year-old black woman, and the third case describes an ulcerating lesion of the perineum and the buttock in a 43-year-old white woman with a long history of endometriosis in an episiotomy scar. Our observations support the notion that clear cell carcinoma arising in extraovarian endometriosis behaves differently from its counterpart in ovarian endometriosis, but more in line with clear cell carcinoma of the endometrium.