Leiomyosarcoma (LMS) is one of the most common subtypes of soft tissue sarcoma (STS) and accounts for approximately 24%. LMS start from cells in a type of muscle tissue called smooth muscle or involuntary muscles - the brain has no conscious control over them. They can be found in the walls of muscular organs like the heart and stomach, as well as in the walls of blood vessels throughout the body. Even though LMS are most common in the uterus, abdomen or pelvis, they can basically start anywhere in the body. Read more Leiomyosarcoma.