Leiomyosarcoma is a malignant (cancerous) tumor that arises from smooth muscle Cells There are essentially two types of muscles in the body - voluntary and involuntary. Smooth muscles are involuntary muscles - the brain has no conscious control over them. Smooth muscles react involuntarily in response to various stimuli. About 1 in 100,000 people get diagnosed with leiomyosarcoma (LMS) each year.LMS is one of the more common types of soft-tissue sarcoma, representing 10 percent to 20 percent of new cases. For example, smooth muscle that lines the walls of the digestive tract causes wave-like contractions (peristalsis) that aid in the digestion and transport of food. Smooth muscles in the salivary glands cause the glands to squirt saliva into the mouth in response to taking a bite of food. Smooth muscle in the skin causes goose bumps to form in response to cold.Leiomyosarcoma is a form of cancer. The term "cancer" refers to a group of diseases characterized by abnormal, uncontrolled cellular growth that invades surrounding tissues and may spread (metastasize) to distant body sites via the bloodstream, the lymphatic system, or other means. Different forms of cancer, including leiomyosarcomas, may be classified based upon the cell type involved, the specific nature of the malignancy, and the disease's clinical course. Leiomyosa usually spreads via the bloodstream. It is very rare to see it in lymphatics.