What is soft tissue sarcoma?

Soft tissue sarcoma is a type of cancer that forms in the soft tissues of the body. Soft tissue is the name for all the supporting tissues in the body, apart from the bones, including fat, muscle, nerves, tendons, deep skin tissue, lymph vessels, blood vessels and tissue around joints. These tissues are called connective tissue, as they support and connect all the organs and structures of the body. 

A soft tissue sarcoma is a rare type of cancer that generally forms as a painless lump (tumour) in any one of these soft tissues. It can develop anywhere in the body, but most commonly in the thigh, shoulder, arm, pelvis and abdomen. Malignant (cancerous) tumours have the potential to spread to other parts of the body through the blood stream or lymph vessels and form another tumour at a new site. This new tumour is known as secondary cancer or metastasis.

Types of soft tissue sarcoma

There are more than 70 types of soft tissue sarcoma. They are named after the abnormal cells that make up the sarcoma.

The most common type in adults is undifferentiated pleomorphic sarcoma (UPS), which is made up of many abnormal spindle-shaped cells. It is aggressive so it often returns or spreads after treatment. Other types of soft tissue sarcoma include:

Adults

• Liposarcoma from fat cells
• Leiomyosarcoma and rhabdomyosarcoma from muscle tissues
• Angiosarcoma from blood and lymph vessels
• Malignant peripheral nerve sheath tumour (MPNST or PNST) from the lining of nerve cells
• Gastro-intestinal stromal sarcoma (GIST) from nerve cells in the gut (treated differently from other types of soft tissue sarcoma)
• Stromal sarcoma from supporting tissues
• Kaposi sarcoma from skin cells.

Children and young adults

• Rhabdomyosarcoma from muscle cells
• Ewing sarcoma (may also start in the bone)
• Synovial sarcoma from cells around joints and tendons.
  
  

Risk factors

The causes of most sarcomas are unknown. However, there are several risk factors, including:

Radiation therapy

There is a very small risk for people who have had radiation therapy to treat other types of cancer. The risk is higher for people who had high doses of radiation therapy at a very young age. Most people who have had radiation therapy in the past will not develop soft tissue sarcoma.

Genetic factors

Some rare, inherited conditions can put people more at risk of soft tissue sarcoma. These conditions include von Recklinghausen disease (also known as neurofibromatosis), Li–Fraumeni syndrome and retinoblastoma.

Most people know if one of these very rare conditions runs in their family, and if so, that they may pass it to their children. If you do not know of this condition in your family, then it is very unlikely that it is present.

A small number of people develop sarcoma due to genetic changes that happen during their lifetime, rather than inheriting a faulty gene.

Chemicals

Some sarcomas may be linked to being exposed to chemicals including vinyl chloride (used to make plastic) and some high-dose herbicides (weedkillers).

Other

Long-term lymphoedema in the body, for example in the legs or arms (swelling from a build-up of lymph fluid) has been linked with angiosarcoma.

Symptoms

Soft tissue sarcoma usually doesn’t cause symptoms in its early stages. As it grows over a period of months, you may develop a painless lump, which may cause pain as it grows and presses on nerves and muscles.

Other symptoms will depend on where in the body the sarcoma is. Sometimes a soft tissue sarcoma may be mistaken for a benign fatty lump (lipoma) or bruise (haematoma). This can delay tests that would help make the right diagnosis.

Most people who develop a painless lump do not have a sarcoma. However, you should see your doctor if you notice the lump is getting bigger, is the size of a golf ball or larger, or is painful or tender.

Diagnosis

If your doctor thinks that you may have a soft tissue sarcoma, they will take your medical history, perform a physical examination (including feeling any lumps) and carry out certain tests. These tests are needed to rule out other conditions.

If the results suggest that you may have sarcoma, your doctor will refer you to a specialist who will carry out more tests, including: 

• Blood tests – including a full blood count to measure your white blood cells, red blood cells and platelets. 
• X-rays – a painless scan of your chest to check your lungs for signs of cancer.
• CT or MRI scans – special painless machines are used to scan and create pictures of the inside of your body. 
• PET scan – you will be injected with a small amount of radioactive glucose (sugar) solution to help cancer cells show up brighter on the scan. 
• Biopsy – removal of some tissue from the affected area for examination under a microscope.