Primary composite angiogenic leiomyosarcoma-epithelioid angiosarcoma of the brain

The authors describe a primary sarcoma of the brain with immunohistochemica l and ultrastructural features of leiomyosarcoma as well as epithelioid hem angiosarcoma. The leiomyosarcomatous component consisted of spindle cells w ith well-developed external lamina, subsarcolemmal densities composed of mi crofilaments, pinocytic vesicles, and abundant intermediate filaments, and showed immunohistochemical reactions for smooth muscle actin. The epithelio id part of the tumor contained scattered cells reactive for alkaline phosph atase as well as CD31 and factor VIII. Many epithelioid cells were lipidize d and remarkably similar to "stromal cells" of a hemangioblastoma. Occasion al Weibel-Palade bodies, indicating endothelial differentiation, were prese nt in scattered neoplastic cells. There were also cells with features inter mediate between endothelium. pericytes and smooth muscle cells, and undiffe rentiated mesenchymal cells. The brain at the periphery of sarcoma showed c onglomerates of well-differentiated capillaries, telangiectasias and small dysplastic arteries, features that raise the possibility of origin of this tumor from a preexisting vascular developmental abnormality.