Causes of Sarcoma
Most often, there is no known cause of sarcoma. However, some causes have been identified:

Kaposi's sarcoma - the only type of soft tissue sarcoma that has a clearly defined cause - the human herpesvirus 8.

High doses of radiation - for example during a previous cancer therapy, are a clear risk factor for soft tissue sarcomas.

Genetic conditions - for some there can be an association with certain genetic conditions.

Risk factors include age, which is associated with cancer in general. Increased risks of sarcoma have also been observed in relation to exposure to certain chemicals, including vinyl chloride, dioxins, and phenoxyacetic herbicides.