Leiomyosarcoma

Leiomyosarcoma is a malignant (cancerous) smooth muscle tumor. A benign tumor originating from the same tissue is termed leiomyoma. While leiomyosarcomas are not thought to arise from leiomyomas, some leiomyoma variants' classification is evolving. About one in 100,000 people are diagnosed with leiomyosarcoma (LMS) each year. LMS is one of the more common types of soft-tissue sarcoma, representing 10 to 20% of new cases. (Leiomyosarcoma of the bone is more rare.) Sarcoma is rare, consisting of only 1% of cancer cases in adults. Leiomyosarcomas can be very unpredictable; they can remain dormant for long periods of time and recur after years. It is a resistant cancer, meaning generally not very responsive to chemotherapy or radiation. The best outcomes occur when it can be removed surgically with wide margins early, while small and still in situ. Smooth muscle cells make up the involuntary muscles, which are found in most parts of the body, including the uterus, stomach and intestines, the walls of all blood vessels, and the skin, so leiomyosarcomas can appear at any site in the body. They are most commonly found in the uterus, stomach, small intestine and retroperitoneum. Uterine leiomyosarcomas come from the smooth muscle in the muscle layer of the uterus. Cutaneous leiomyosarcomas derive from the pilo-erector muscles in the skin. Gastrointestinal leiomyosarcomas might come from smooth muscle in the GI tract, or alternatively, from a blood vessel. At most other primary sites—retroperitoneal extremity (in the abdomen, behind the intestines), truncal, abdominal organs, etc.—leiomyosarcomas appear to grow from the muscle layer of a blood vessel (the tunica media). Thus, a leiomyosarcoma can have a primary site of origin anywhere in the body from a blood vessel. The tumors are usually hemorrhagic and soft and microscopically marked by pleomorphism, abundant (15–30 per 10 high-power fields) abnormal mitotic figures, and coagulative tumor cell necrosis.