Epithelioid leiomyosarcoma of the uterus with oncocytic change

We report on a rare case of epithelioid leiomyosarcoma of the uterus with o ncocytic change and aggressive clinical behavior. The tumor arose in the le ft lateral wall of the uterus and measured 22 cm in greatest dimension. His tologically, it consisted of solid sheets of round and polygonal cells disp laying a homogeneously eosinophilic cytoplasm and pleomorphic nuclei with p rominent nucleoli. Six mitotic figures were found per 10 high-power fields in the most mitotically active areas, and focal tumor cell necrosis was pre sent elsewhere. Under electron microscopy, numerous normal-appearing mitoch ondria and occasional bundles of microfilaments with focal densities were n oted in the tumor cell cytoplasm, and poorly-formed external basal lamina a nd occasional pinocytic vesicles were found on the cell membrane of some tu mor cells.