Causes

Sarcomas go by a variety of names, depending on the tissue in which they originate. Locations of sarcomas and their names include:

• Bones. These include osteosarcomas, which occur primarily in growing bone tissue; chondrosarcomas, which occur in cartilage; and Ewing's sarcomas, which arise primarily in immature tissue in bone marrow. Osteosarcomas and Ewing's sarcomas occur most often in children, adolescents and young adults, ages 10 to 25.

• Muscle. There are two types of muscles: skeletal and smooth. Skeletal muscles move bones and are under your voluntary control. You can't control smooth muscles, which line blood vessels and organs such as the uterus and gastrointestinal tract.

• Sarcomas that arise from muscles include rhabdomysarcomas, which occur in skeletal muscles, most commonly in your arms and legs. There are multiple subtypes of rhabdomyosarcoma, including embryonal sarcomas, which tend to occur in the head, neck and genitourinary tract of children ages 4 and younger, and alveolar sarcomas, which occur in the arms, legs, head and neck of children. Leiomyosarcomas occur in the smooth muscles, most commonly in the uterus, gastrointestinal tract or lining of blood vessels.

• Blood vessels. These include angiosarcomas, which most commonly occur in the blood vessels of your arms, legs, head and trunk; infantile hemangiopericytomas, which generally occur in the blood vessels of the arms, legs, trunk, head and neck of children ages 4 and younger; and Kaposi's sarcoma, a tumor of the blood vessel walls, which occurs in people with immune deficiencies such as HIV/AIDS.

• Lymph vessels. Called lymphangiosarcomas, this type occurs in the lymph vessels, most commonly in your arms or legs.

• Synovial tissue. A type called synovial sarcomas occurs in proximity to joints and in tendon sheaths of your legs.

• Nerves. Neurofibrosarcomas occur in the peripheral nerves of your arms, legs and trunk.

• Fat. Liposarcomas occur in the fatty tissues, often in your arms, legs and trunk.

• Fibrous tissue. These include fibrosarcomas, which occur in your arms, legs and trunk; malignant fibrous hystiocytomas, which occur in your legs; and dermatofibrosarcomas, which occur in your trunk.

• Mesothelial tissues. These tissues provide a protective lining for certain organs, such as your lungs, heart and intestines. Malignant tumors that arise from these tissues are called mesotheliomas and most commonly occur in your lungs.

In general, no one knows for sure what causes most bone or soft tissue sarcomas. Known causes include asbestos for most cases of mesothelioma, and viruses for Kaposi's sarcoma in people with defective immune systems. Adults with Paget's disease of bone, which involves abnormal development of new bone cells, may be at increased risk of osteosarcoma. In a few cases, sarcomas may be hereditary, such as in Li-Fraumeni syndrome or in families with neurofibromatosis. Li-Fraumeni syndrome is a condition of early breast cancer associated with soft tissue sarcomas and other tumors. Neurofibromatosis results in developmental changes in the nervous system, causing nerve tumors. Other abnormalities associated with neurofibromatosis include skin changes and bone deformities.

Factors that may lead to increased risk of sarcoma are exposure to high doses of herbicides that contain the chemical phenoxyacetic acid, wood preservatives, which contain chlorophenols, as well as large doses of radiation.