Classification of fibroma and thecoma of the ovary.An ultrastructural study

Abstract

The fine structure of 6 ovarian neoplasms, 5 fibromas, and 1 thecoma, as diagnosed by the light microscope, was studied. Based on such features as cellular shape, organelle composition, and nuclear patterns, the cells apparently formed a morphological continuum, comparable to that observed in the normal ovarian cortical stroma. The cells varied from a spindly fibroblast-like type with a thin elongated nucleus and scanty cytoplasm to a polygonal theca interna type with a large round nucleus, a prominent nucleolus, and abundant cytoplasm containing abundant endoplasmic reticulum, well-developed Golgi apparati, numerous mitochondria, and a variable number of lipid droplets. Intermediate-type cells increasing in plumpness and structural complexity bridged the gap between the two extreme varieties. The proportions of the spindly, intermediate, and polygonal cell types in the different neoplasms varied according to their degree of cellularity and collagen content: the first type was most frequently seen in the heavily collagenized and the second in the less heavily collagenized neoplasms. The finding in this study support the view that the ovarian fibroma and thecoma are not two different neoplasms, but are variants of a single neoplasm with a common origin from the ovarian stroma.