Non-Uterine Leiomyosarcoma

Leiomyosarcoma is a cancer of smooth muscle cells. Smooth muscle cells make up the involuntary muscles, which are found in most parts of the body: in uterus, stomach and intestines, walls of all blood vessels, skin [the muscles that give you ‘goose bumps’]. This muscle is involuntary muscle, you cannot make these muscles move by thinking about them.

GISTs [Gastrointestinal Stromal Tumors] are a special kind of tumor, that used to be considered a kind of Leiomyosarcoma, coming from a particular smooth muscle cell in the stomach/small intestine. We mention these first and separately because there has been a dramatically good advance in treating some of these tumors with a new designer drug. See the separate page on GIST tumors and Glivec/Gleevec. Any Gastrointestinal “sarcoma” or GI LMS should be tested for CD 117 [also called Ckits] protein by an experienced laboratory. This is potentially life-saving information.


Leiomyosarcoma accounts for 7 to 11 percent of all soft tissue sarcomas among adults and children.

Distinct Clinical Features

Leiomyosarcomas apparently arise between the muscularis propria and muscularis mucosa layers of the bowel wall, though the exact histological source is in question. The tumors generally are made up of spindle-shaped cells and have a high cellularity. With high-grade tumors, necrosis often is present.

When considering all primary malignancies of the small bowel, adenocarcinomas tend to occur more proximally, whereas carcinoids, lymphomas, and leiomyosarcomas occur more distally. Depending on the study reviewed, the primary sites of occurrence of leiomyosarcomas are divided equally between the stomach and the small intestine. As many as 50% of the leiomyosarcomas occurring in the small intestine are found in the ileum. Relatively few leiomyosarcomas have been found in the esophagus, colon, or rectum.

The natural history of this tumor involves local growth initially, with much of its growth being extraluminal; thus, obstruction occurs late. Multiple primary sites are unusual. Often, as the size of the leiomyosarcoma increases, necrosis and bleeding follow. This leads to the most common presenting feature in symptomatic patients, bleeding, which often is massive.


The usual treatment for a leiomyosarcoma is surgery, wherever possible, to remove the tumour. This may be followed by radiotherapy to reduce the chance of the cancer coming back. Chemotherapy is also used for some leiomyosarcomas. This may be to try to reduce the chances of the leiomyosarcoma coming back, or to treat a leiomyosarcoma that has spread.