Lipid cell tumor of the ovary: an ultrastructural study.

An ovarian lipid cell tumor without Reinke's crystalloids in a woman with secondary amenorrhea, minimal hirsutism, and elevated 17-ketosteroid excretion was studied by light and electron microscopy. Tumor cells were found in small clumps or scattered singly within a collagenous matrix. The cytoplasm of the tumor cells contained abundant smooth endoplasmic reticula, numerous mitochondria with tubular cristae, lipid droplets, lysosomal dense bodies, and concentric membranous whorls, characteristic of steroidogenic cells. In addition, "peripheral canalicular systems" were found at the outer margins of the nests of the tumor cells. These "peripheral canalicular systems" were bordered by the cell membranes and the surrounding collagenous stroma into which microvilli projected. Since the intercellular canalicular system present between the tumor cells was continuous with the "peripheral canalicular system," both systems probably have a common function related to steroid metabolism. The intercellular and "peripheral" canalicular systems and cytoplasmic microfilaments found in this tumor suggest that this ovarian lipid cell tumor was derived from the ovarian stroma.