[Estrogen production in epithelial tumors of the ovary--identification of estrogen-synthesizing cells].

Morphological, fine structural and enzyme histochemical investigation of common epithelial tumors of the ovary was aimed at identifying the estrogen-synthesizing cells in the stroma of the tumor. Histological changes in cell condensation or "thecosis" and cell enlargement or "luteinization" were commonly observed in the stromal area of the tumor. Two types of stromal cells were found by electron microscopic study; one had characteristic organelles of steroid hormone-producing cells, and the other had a similar cytoplasmic structure to that of fibroblastic cells. Both types of cells had lipid droplets in the cytoplasm. The former seemed to be transformed from the latter. Steroidogenesis-related enzymes such as 3 beta-hydroxy steroid dehydrogenase (HSD) and 17 beta-HSD were demonstrated in the stromal cells. Electron microscopy revealed that these enzymes were localized at the intercrystal space and inner membrane of mitochondria with tubular crystal. These findings indicated that thecosis appeared in the stroma of the epithelial tumor, and the stromal cell acquired estrogen-producing potential.