Clear cell (mesonephroid) tumors of the ovary with characteristics resembling endodermal sinus tumor.

Twenty-five ovarian clear cell tumors and six endodermal sinus tumors were studied by histochemical, immunohistochemical, and ultrastructural methods. The results of the study indicate that some clear cell tumors contain periodic acid Schiff (PAS) positive and diastase resistant hyaline globules, and also basement membrane-like material, which have been previously considered as being observed only in endodermal sinus tumor. In view of this, we would like to emphasize the importance of the presence of the various histological patterns observed in endodermal sinus tumor, in addition to the classical perivascular formations (Schiller-Duval bodies) and the presence of alpha-fetoprotein (AFP), as diagnostic features of endodermal sinus tumor. On the other hand, the presence of glycogen, abundant rough endoplasmic reticulum stacked in parallel rows, and a more uniform histological pattern are indicative of clear cell (mesonephroid) tumor of the ovary.