Vaginal hemangiopericytoma: a light microscopic and ultrastructural study.

A case of a vaginal hemangiopericytoma in a 20-year-old woman was studied by light and electron microscopy. The neoplastic cells had round-to-oval nuclei with one or two nucleoli; fine chromatin; a foamy, cyanophilic cytoplasm; and an increased nuclear cytoplasmic ratio. Light microscopically, the tumor was composed of spindle-shaped or round cells proliferating around vascular spaces. Mitotic figures, necrosis, and hemorrhage were difficult to find. Electron microscopically, the neoplastic cells occurred in clusters, each of which was enclosed by a basal lamina. The cytoplasm contained abundant free ribosomes, flattened elements of rough endoplasmic reticulum, small Golgi apparatus, round or elongated mitochondria, lysosomes, glycogen particles, and sometimes pinocytotic vesicles and bundles of microfilaments with large dense spots. Desmosomes were also seen. In addition, the cytoplasmic process of the benign vascular pericytes was directly in contact with the neoplastic cells which had varying degrees of cytodifferentiation. The neoplastic cells in this lesion are consistent with an origin from pericytes, confirming the findings of this neoplasm when it arose in other sites.