Clear cell carcinoma of the sigmoid mesocolon: a tumor of the secondary müllerian system.

Clear cell carcinoma was found in the sigmoid mesocolon of a 54-year-old woman, 6 years after the removal of all ovarian tissue. This tumor is of müllerian origin. In addition to the müllerian structures proper--the fallopian tubes, uterus, cervix, and upper vagina--a "secondary müllerian system" is present diffusely throughout the pelvis and lower abdomen. This case represents a tumor of the secondary müllerian system.