Ovarian yolk sac tumor arising from an endometrioid carcinoma.

A yolk sac tumor that arose within an ovarian endometrioid adenocarcinoma in a 50-year-old woman is described. The tumor had typical microscopic features, stained immunohistochemically for alpha-fetoprotein, and was associated with an elevated serum alpha-fetoprotein level when metastases appeared. This is the fourth case in which a yolk sac tumor has been reported to develop from a somatic carcinoma and the second in which this tumor has been associated with epithelium of endometrioid type. Tumor heterogeneity or neometaplasia may account for the origin of a tumor of germ cell type from a carcinoma of somatic origin.