Leiomyosarcoma (leiomyosarcoma; from the Greek. Leios - smooth; mys, myos - muscle + sarcoma) is a malignant tumor originating from smooth muscle fibers. More often than in other organs, it is found in the uterus, less often in the stomach, intestines, rectum, bladder, kidneys. Tumor is rather dense or soft, white or pink in color, with hemorrhages, foci of necrosis. Histologically, leiomyosarcoma is variable. Typical leiomyosarcomas are similar to leiomyomas, differentiated from the latter by the number of mitoses and infiltrating growth. Most leiomyosarcomas have pronounced cellular atypism, built of bundles of large spindle-shaped or rounded cells with massive hyperchromic nuclei and less acidophilic than normal protoplasm; there are ugly giant cells. Many atypical mitoses. Sometimes cell atypism is so great that it is difficult to establish the origin of a tumor from smooth muscles. Leiomyosarcoma (at a late stage of the disease) metastasizes to the liver, kidneys, lungs, and peritoneum. Surgical treatment.