Poorly differentiated (small cell) carcinoma of the ovary in young women: evidence supporting a germ cell origin.

The clinical and pathologic features, including immunohistochemistry and electron microscopy, of six cases of poorly differentiated carcinoma of the ovary (small cell carcinoma) are presented. These tumors occurred in six young patients ranging in age from 10 to 24 years. Two patients had hypercalcemia. All tumors were unilateral, and four patients had advanced stage disease at presentation. Histologic features included sheets, nests, and cords of cells in a fibrous stroma, focal microcysts, and a dimorphic population of small and large cells. Eosinophilic, hyaline globules occurred in five cases, intercellular basement membrane-like substance in two cases, and glycogen in all cases. Five of six cases stained strongly for cytokeratin and vimentin; intracytoplasmic laminin was identified in three cases; and three cases were believed to show faint positivity for alpha-1-antitrypsin. Stains for alpha-fetoprotein were negative. Ultrastructural examination of two cases showed granular material in dilated rough endoplasmic reticulum, intermediate filaments, intracytoplasmic dense globules, maculae adherens, and extracellular basement membrane-like material. All of the cases proved rapidly fatal despite various therapies, as did a histologically similar testicular tumor that was admixed with seminoma and teratoma. We interpret these findings to indicate that this ovarian cancer is most likely of germ cell origin, and it may be related to yolk sac tumor, although it is clearly distinct from the classical yolk sac tumor.