Soft tissue sarcomas are cancers that develop from cells in the soft, supporting tissues of the body. They can occur in soft tissues such as fat, muscle, nerves, fibrous tissues, blood vessels or in any of the other tissues that support, surround and protect the organs of the body.
Soft tissue sarcomas can develop in any part of the body. Most of them develop in the arms and legs, but they can also develop in specific organs such as the womb (uterus), stomach, skin and small bowel. Less commonly, they may occur in the head and neck.
Some types of sarcoma occur in children, teenagers and young adults, but generally they are more likely to develop in people over the age of 30.
Although the causes of soft tissue sarcomas are unknown, research is going on to try to find out more. Sarcomas, like other cancers, are not infectious and can’t be passed on to other people.
Risk Factors for Developing Soft Tissue Sarcomas
Sarcomas can occur at any age but are more common as people get older. About two-thirds of all soft tissue sarcomas are diagnosed in people over 50.
Most sarcomas are not caused by an inherited faulty gene that can be passed on to other family members. Members of your family are not likely to have an increased risk of developing a soft tissue sarcoma because you have one. However, people who have some rare inherited genetic conditions are more at risk of developing a sarcoma. These conditions include neurofibromatosis, Gardner’s syndrome, Li-Fraumeni syndrome andretinoblastoma. You would normally know if any member of your family had one of these conditions, and their doctor would check them regularly for any sign of a sarcoma.
Previous radiotherapy treatment
Very rarely, a soft tissue sarcoma will occur in a part of the body that has previously been treated with radiotherapy for another type of cancer. The sarcoma will not usually develop until at least 5-10 years after the radiotherapy treatment. To reduce the risk, radiotherapy is very carefully planned. Improvements in the way radiotherapy is given mean that the risk of developing a sarcoma is very small.
Exposure to chemicals
The development of some sarcomas may be linked to exposure to some types of chemicals. The chemicals include: vinyl chloride, which is used for making plastics; some types of herbicides (weedkillers); and dioxins, which are a waste product produced during the manufacture of chemicals and fertilizers.
There is no evidence that an injury can cause a soft tissue sarcoma to develop. It’s possible that an injury may draw attention to a sarcoma that was already there and not causing any symptoms, but the sarcoma will have taken many years to develop.
Types of soft tissue sarcoma
There are many types of soft tissue sarcoma, and they tend to grow and develop differently. The most common types are described on this page. Your doctor or specialist nurse can tell you more about which type you have. Each type of sarcoma is named after the type of cell it started from, rather than the part of the body where it started to grow.
Fat tissue tumors
Sarcomas that start in the body’s fat cells are called liposarcomas. They can grow anywhere in the body and most commonly affect people aged 50-65. Some grow very slowly, taking many years to develop, whereas others grow more quickly.
Muscle tissue tumors
There are two different types of muscle tissue in the body: smooth and skeletal.
Smooth muscle sarcomas
Smooth muscle forms the walls of internal organs such as the womb (uterus), stomach, intestine and blood vessels. The muscle causes these organs to contract, which happens without our control. Smooth muscle is also called involuntary muscle. Sarcomas that develop in smooth muscle are called leiomyosarcomas. They are one of the more common types of sarcoma and can occur anywhere in the body, especially in the back of the abdominal area (retroperitoneum). Leiomyosarcomas are less often found in the deep, soft tissues of the legs or arms. They tend to occur in adults, particularly in the elderly.
Skeletal muscle sarcomas
Skeletal muscles are the active muscles in our arms and legs or other parts of the body that we control. They are voluntary muscles and sometimes called striated muscles because the cells look stripy when examined under a microscope. Sarcomas that grow in the voluntary muscles of the body are called rhabdomyosarcomas. They occur mostly in the head and neck, but also in organs such as the bladder, vagina and the arms or legs. Rhabdomyosarcomas are more commonly diagnosed in children than in adults.
Peripheral nerve tumors
The nervous system in the body is divided into two parts: the central nervous system, which is made up of the brain and spinal cord; and the peripheral nervous system, which consists of all the nerves that run throughout the body. Sarcomas of the peripheral nerves develop in the cells that cover the nerves. They’re known as malignant peripheral nerve sheath tumors (MPNST) and can occur anywhere in the body. There are different types of MPNSTs, including malignant schwannomas and neurofibrosarcomas. They most commonly occur in people who have a rare genetic disorder called neurofibromatosis (von Recklinghausen’s disease).
Fibrous tissue tumors
Fibrous tissues join together the inner structures of the body, for example, they join muscles to bones. This tissue is made up of cells called fibrocytes. A sarcoma of the fibrous tissue is called a fibrosarcoma. They are most commonly found on the arms, legs or trunk, but can occur deeper in the body. They can occur at any age but are more commonly seen in people aged 20-60. Most people first notice them as a painless, firm lump.
This is a type of fibrosarcoma. It was previously called malignant fibrous histiocytoma (MFH). It’s not clear which type of cell it starts from. Myxofibrosarcomas can affect any part of the body, but most commonly occur in the arms or legs.
These tumors are sometimes known as Desmoid tumors. They are classified as benign tumors, not cancer. They’re sometimes said to be halfway between a fibrosarcoma and a benign fibroma (a non-cancerous tumor of fibrous tissue). Desmoid tumors don’t tend to spread to other parts of the body, but can spread into nearby tissues, and so are usually treated in a similar way to cancerous sarcomas.
Joint tissue tumors
Soft tissue sarcomas that develop very close to the body’s joints are known as synovial sarcomas. They commonly develop near, but not inside, joints such as the knee or elbow, but they can occur in any part of the body. They usually appear as hard lumps and are more common in children and young adults.
Blood and lymph vessel tumors
Sarcomas that start from the cells that make up the walls of blood or lymph vessels are called angiosarcomas. Haemangiosarcomas develop from blood vessels and lymphangiosarcomas develop from the lymph vessels. Angiosarcomas sometimes occur in a part of the body that has been treated with radiotherapy many years before.
Other types of sarcoma
Gastrointestinal stromal tumors (GIST)
These are the most common type of soft tissue sarcoma and develop in nerve cells in the walls of the digestive system. The digestive system is often called the gastrointestinal (GI) tract. This type of tumor may also be called GI stromal sarcoma. GISTs behave differently from other types of sarcoma and are treated very differently.
Kaposi’s sarcoma (KS)
Although Kaposi’s sarcoma is a type of sarcoma, it differs from other sarcomas in the way it develops. It starts from cells in the skin. Colored patches or lumps can develop in the skin, mouth, lymph nodes or internal organs such as the lung, liver or spleen. Kaposi’s sarcoma can affect people with a weakened immune system, including people with HIV and Aids. Other types can affect people of Jewish, Italian and West African origin. Kaposi’s sarcoma is treated differently from other types of soft tissue sarcoma.
Ewing’s tumors are a type of bone sarcoma, but about a third of all Ewing’s tumors develop in the soft tissue and are known as extraosseous Ewing’s tumors. Soft tissue Ewing’s sarcomas tend to behave differently from other soft tissue sarcomas and are usually treated in a similar way to bone sarcomas.
Rarer types of sarcoma
There are other much rarer types of sarcoma than those we have already listed. These include:
• alveolar soft part sarcoma
• dermatofibrosarcoma protuberans (DFSP)
• desmoplastic small round cell tumor
• epithelioid sarcoma
• extraskeletal myxoid chondrosarcoma
• giant cell fibroblastoma (GCF).
Our cancer support specialists can give you information about these rarer types of sarcoma.
Soft tissue sarcomas in children
Soft tissue sarcomas can occur in children, particularly some types of rhabdomyosarcoma. Their symptoms and treatment may differ from those in an adult with the same sarcoma.