Leiomyosarcoma, or LMS, affects an estimated four people out of one million, according to the National LeioMyoSarcoma Foundation. LMS is such a rare form of cancer that doctors have limited research to guide treatment, and patients are typically referred to sarcoma specialists.
Leiomyosarcoma is a type of soft tissue sarcoma, causing malignant tumors that form in connective tissues, such as tendons, muscles and fats, states the National Organization for Rare Disorders. Doctors diagnose about 15,000 cases of soft tissue sarcoma every year, but LMS only accounts for roughly 7 to 11 percent. The severity and prognosis of LMS depends on where it starts, how far it spreads and how early it is diagnosed. Tumorous growths often spread aggressively from connective tissues to surrounding organs, such as the liver.