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. From Wikipedia
