Leiomyosarcoma of the Colon and Rectum

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Early detection of leiomyosarcoma of the colon and rectum is crucial because the cancer metastasizes (spreads) in more than half of patients. However, early diagnosis often does not occur until after complications such as bleeding or obstruction appear.

What Is Leiomyosarcoma?

Cancerous tumors of connective tissue are called "sarcomas." Cartilage, fat, blood vessels, nerves, muscles, and bones are all considered connective tissue. Sarcomas are further divided into two groups: bone tumors and soft tissue sarcomas. Soft tissue sarcomas, specifically leiomyosarcomas, occur in the colon and rectum.

"Leio-" means "smooth" and "myo-" means "muscle." So, "leiomyosarcoma" literally means a cancer of smooth muscle. The colon has three layers of this type of muscle, which work together to move waste through the digestive tract.


Symptoms of leiomyosarcoma include bleeding and pain. The average age at diagnosis is 60.


The exact causes of leiomyosarcoma are not known, but studies have shown that there are genetic and environmental risk factors associated with it. Certain inherited conditions that run in families could possibly increase the risk of developing leiomyosarcoma. High-dose radiation exposure, such as radiotherapy used to treat other types of cancer, has also been linked to leiomyosarcoma and it is possible that exposure to certain chemical herbicides might increase the risk of developing this disease, but a direct association has not been proven.


Leiomyosarcomas are extremely uncommon and account for less than two percent of all colorectal cancers.


After diagnosis, your tumor will be staged to determine how far cancer has advanced. This is important because treatment varies depending on the stage. The stage is determined by the size of the tumor, whether the tumor has spread to nearby lymph nodes, whether the tumor has spread elsewhere in the body, and what the cells look like under the microscope.

Tumors are staged using numbers I through IV. The higher the number, the more the tumor has advanced. Stage IV Leiomyosarcoma means it has involved either lymph nodes or has spread to distant parts of the body.
The outlook for patients with leiomyosarcoma varies. It depends on the location and size of the tumor and its type and extent of spread. Some patients with low-grade tumors or with tumors that have not spread beyond Stage I have had excellent prognoses. There are numerous long-term survivors from this group. In general, high-grade tumors that have spread widely throughout the body have less favorable survival rates.

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