A rare soft tissue cancer that arises from smooth muscle cells which form the involuntary muscles. Smooth muscle cells can occur in the skin, uterus, stomach, intestine and blood vessel walls. The main location for these tumors is in the uterus, retroperitoneum, pelvis and large blood vessels such as the inferior vena cava. Symptoms depend on the size and location of the tumor. See also Leiomyosarcoma
