Clear cell carcinoma of the uterine endocervix with an in situ component

In the past all clear cell carcinomas of the female genital tract were thought to arise from mesonephric remnants. Recently increasing evidence has related their origin to müllerian rather than mesonephric epithelium. One of the main reasons that has been advanced to support their mesonephric origin has been their occurrence in the uterine cervix and vagina, sites of mesonephric remnants. However, no clear evidence for mesonephric origin of clear cell carcinoma of the cervix and vagina has been ever provided. In contrast, there is substantial evidence that diethylstilbestrol-related clear cell carcinomas of the cervix and vagina are müllerian in origin. We report here a case of an exophytic clear cell carcinoma with an in situ component, involving the endocervical epithelium. The in situ lesion clearly indicates müllerian origin of the tumor, which occurred in the absence of prenatal exposure to diethylstilbestrol. This supports the general agreement that clear cell carcinomas of the cervix are müllerian in origin, whether diethylstilbestrol-related or not.