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<unk> s can appear at any site in the body. They are most commonly found in the uterus, stomach, small intestine and retroperitoneum. Uterine<unk> s come from the smooth muscle in the muscle layer of the uterus. Cutaneous<unk> s derive from the pilo-erector muscles in the skin. Gastrointestinal<unk> s 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<unk>  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. The differential diagnosis, which includes spindle cell carcinoma, spindle cell melanoma, fibrosarcoma, malignant peripheral nerve sheath tumor and even biphenotypic sinonasal sarcoma, is wide.
Leiomyosarcoma
Uterine fibroid  s  1
Uterine sarcoma
Adenomyoma
Endometrial stromal sarcoma
Endometrial stromal tumour
Piloleiomyoma
Uterine adenosarcoma