Epithelioid leiomyosarcoma of the uterus with oncocytic change.

We report on a rare case of epithelioid leiomyosarcoma of the uterus with oncocytic change and aggressive clinical behavior. The tumor arose in the left lateral wall of the uterus and measured 22 cm in greatest dimension. Histologically, it consisted of solid sheets of round and polygonal cells displaying a homogeneously eosinophilic cytoplasm and pleomorphic nuclei with prominent nucleoli. Six mitotic figures were found per 10 high-power fields in the most mitotically active areas, and focal tumor cell necrosis was present elsewhere. Under electron microscopy, numerous normal-appearing mitochondria and occasional bundles of microfilaments with focal densities were noted in the tumor cell cytoplasm, and poorly-formed external basal lamina and occasional pinocytic vesicles were found on the cell membrane of some tumor cells.