Risks and causes of soft tissue sarcomas

Your risk of developing cancer depends on many things, including:

• age
• genetics
• lifestyle
• environmental factors

Risk factors

Soft tissue sarcomas are rare cancers. Around 3,300 people were diagnosed with soft tissue sarcoma in 2010 in the UK. 

We don't know what causes most soft tissue sarcomas. But some factors may increase your risk of developing it.

Having any of these risk factors does not mean that you will develop cancer.

Age

Soft tissue sarcomas can develop in people of all ages, but like most cancers, the risk increases as we get older. Around 40 in 100 soft tissue sarcomas (40%) are diagnosed in people aged 65 or older.

Sarcoma can develop in children and young people. Almost 10 in 100 tumours (10%) are diagnosed in people younger than 30. 

Previous radiotherapy treatment

Less than 1 in every 100 (1%) of people who had radiotherapy for other cancers might get a sarcoma in the treatment area years later. This is because the radiation can affect healthy tissue in the treated area.

The increase in risk depends on the:

• person's age
• location of the cancer
• dose of the radiotherapy

People who had high doses of radiotherapy as children have the biggest increase in risk. But different studies give different levels. Combining chemotherapy with radiotherapy may increase the risk further.

In adults, doctors link sarcomas caused by previous radiotherapy to treatment for cancers such as:

• breast cancer
• lymphoma
• women's cancers
• prostate cancer
• unrelated types of sarcoma
• head and neck cancers
• bowel cancer
• germ cell tumours

In children, it is linked to previous radiotherapy treatment for:

• retinoblastoma
• Ewing sarcomas
• rhabdomyosarcoma
• Hodgkin lymphoma
• brain tumours
• Wilms tumour

If you are having radiotherapy for cancer, it is important to keep in mind the benefit of the treatment. Treating the cancer is essential. Doctors balance this against the small risk of getting a sarcoma in the future. Radiotherapy treatment is planned very precisely. Newer types of radiotherapy cause less damage to healthy tissues.

Radiation

Ionising radiation in the environment can also increase the risk of sarcoma. This was for example during the atomic bomb explosions in Japan during World War 2. The rates of sarcoma were higher under these people.

Exposure to chemicals

Several chemicals are thought to possibly increase the risk of some types of sarcoma. This might be in situations where people were exposed to high levels in their job over many years.

The number of sarcoma cases in the studies is usually very small. This means it is hard to say how big the risk from these chemicals is for people who work with them.

The International Agency for Research on Cancer looks at the evidence for substances and their links with causing cancer. They say the following chemicals have limited evidence for causing soft tissue sarcoma:

• radioiodines, including iodine-131
• polychlorophenols
• 2,3,7,8-tetrachlorodibenzo-para-dioxin

Family history

Some types of rare genetic conditions can increase your risk of getting a sarcoma. 

A genetic condition can appear in a family that has not had it before, but this is very rare. You are likely to know if any of these conditions run in your family. These include:

Neurofibromatosis 

This is a genetic disease. Non cancerous (benign) tumours form in the nerves under the skin and in other parts of the body.

It increases the risk of getting a rare type of sarcoma called a malignant peripheral nerve sheath tumour (MPNST). 

Li Fraumeni syndrome  

This is a genetic syndrome. It causes several different types of cancer to occur in affected families. This is because of a change (mutation) in the TP53 gene that stops tumours from growing. It's sometimes called a family cancer syndrome.

Families with Li Fraumeni syndrome have a higher risk of developing:

• soft tissue sarcoma
• other cancers

Retinoblastoma 

This is a type of inherited eye cancer. It is nearly always diagnosed in childhood.

Children who have had retinoblastoma have an increased risk of developing a soft tissue sarcoma in the future. 

The most common types are:

• leiomyosarcoma
• fibrosarcoma
• rhabdomyosarcoma

The radiotherapy given as treatment for retinoblastoma forms part of the increased risk. These children also have an increased risk of getting a type of bone cancer called osteosarcoma.

Infections and lowered immunity

In the UK, Kaposi's sarcoma is a rare type of soft tissue sarcoma. It develops from cells in the lining of the blood and lymph vessels. Kaposi's sarcoma is caused by Human Herpes Virus 8 infection (HHV8). It is also known as Kaposi's sarcoma associated herpesvirus (KSHV). 

Many people have HHV8, and most do not develop Kaposi's sarcoma. But this virus can sometimes cause Kaposi's sarcoma in people with lowered immunity, mainly in people with:

• HIV
• AIDS

People taking medicines to suppress their immunity also have a higher risk of getting Kaposi's sarcoma. This is usually after an organ transplant. 

An infection called Epstein Barr virus (EBV) has been linked with leiomyosarcoma. This is in children and young people with HIV or AIDS. It's also been linked to leiomyosarcoma in adults taking medicines to suppress immunity after a transplant. There is also some research that shows people developing angiosarcoma after kidney transplants.

Arm and leg swelling

Radiotherapy and surgery for breast cancer can cause long term swelling (lymphoedema) of the arm. Radiotherapy or surgery to the pelvic area or genital area can cause swelling of the leg.

Women with chronic arm lymphoedema following breast removal (mastectomy) can get angiosarcoma. This is a type of sarcoma that usually develops in the arm. It is very rare and is also known as Stewart-Treves syndrome. It takes many years to develop. 

More rarely, angiosarcoma may occur in the leg in people who have chronic lymphoedema of the leg.

Umbilical or inguinal hernias

A Ewing sarcoma is more likely with children born with:

• a hernia of the tummy button (a congenital umbilical hernia)
• a hernia at the top of the leg (an inguinal hernia)

An umbilical hernia is caused by a weakness of the muscle around the belly button. An inguinal hernia is a weakness of the muscle in the groin area. It is not clear why hernias increase the risk of sarcoma.

Possible risk factor

Women who are very overweight (obese) may have a higher risk of sarcomas of the womb. This is compared to women who are not overweight.

Other possible causes

Stories about potential causes are often in the media, and it isn't always clear which ideas are supported by evidence. There might be things you have heard of that we haven't included here. This is because either there is no evidence about them, or it is less clear.

Injuries

Sometimes people think that an injury has caused a cancer. There's no evidence that an injury of any kind can cause a sarcoma. But an injury may draw attention to a sarcoma that was already there. This is usually if the person has x-rays or scans.

In most cases where people think an injury is responsible, the injury has only happened recently. It is unlikely to be linked to the cancer.

More information

You can read more detailed information on soft tissue sarcoma risks and causes in the Cancer Research UK Statistics section.