Dictionary.net

A rare tumor of the female genital tract, most often the ovary, formerly considered to be derived from mesonephric rests. Two varieties are recognized: (1) clear cell carcinoma, so called because of its histologic resemblance to renal cell carcinoma, and now considered to be of muellerian duct derivation and (2) an embryonal tumor (called also ENDODERMAL SINUS TUMOR and yolk sac tumor), occurring chiefly in children. The latter variety may also arise in the testis. (Dorland, 27th ed)