Decorative image

Risks and causes

Read about the risks and causes of soft tissue sarcomas.

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

We don’t know what causes most soft tissue sarcoma cancers. But there are some factors that may increase your risk of developing it.

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

Soft tissue sarcomas can develop in people of all ages, but as we get older our risk goes up. 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. Just over half of these are a specific type called rhabdomyosarcoma. This type develops most often in children aged 4 or younger.

Radiotherapy treatment for other cancers can sometimes cause a sarcoma in the treatment area years later. This is because the radiation can affect healthy tissue in the treated area.

The amount of increase in risk depends on the age of the person and the dose of the radiotherapy. People treated as children with high doses of radiotherapy have the biggest increase in risk although different studies give different levels. Combining chemotherapy with radiotherapy may increase the risk further.

If you are having radiotherapy for cancer, it is important to keep in mind how much good the treatment is doing you. Treating the cancer is essential and doctors balance this against the small risk of getting a sarcoma in the future. Radiotherapy treatment is planned very precisely.

Radiation in the environment can also slightly increase the risk of sarcoma. People exposed to the atomic bomb explosions in Japan at the end of World War 2 had higher rates of developing these cancers.

People who have had a previous cancer have a small increase in their risk of developing a soft tissue sarcoma.

Some of this can be explained by treatments such as radiotherapy or by swelling (lymphoedema) after breast cancer treatment. And some of these tumours may be caused by other factors such as gene changes linked to sarcoma as well as other cancers.

The increase in risk is more with some cancers than others including cancers of the breast, kidney, bladder, skin, womb and ovary.

People who had cancer as a child have a higher risk of developing soft tissue sarcoma than the general population. The risk is highest in people who had brain tumours, spinal cord tumours, Hodgkin lymphoma, Wilm's tumour, soft tissue sarcoma or bone sarcoma.

Several chemicals are thought to increase the risk of some types of sarcoma. The number of cases of sarcoma in the studies is usually very small. These chemicals include:

  • vinyl chloride
  • dioxins
  • chlorophenols

Some types of rare genetic conditions can increase your risk of getting a sarcoma. You are likely to know if any of these conditions run in your family.

A genetic condition can crop up in a family that has not had it before but this is very rare. These include:

Neurofibromatosis 

This is a genetic disease in which 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 very rare type of sarcoma called a malignant peripheral nerve sheath tumour (MPNST). Less than 5 in 100 people with neurofibromatosis (5%) will have a MPNST at some point in their life. Neurofibromatosis is also called von Recklinghausen disease.

Li Fraumeni syndrome 

A genetic syndrome that causes several different types of cancer to occur in affected families. It’s sometimes called family cancer syndrome.

Families with Li Fraumeni syndrome have a higher risk of breast cancer, brain tumours, leukaemias and other cancers. They also have a higher risk of developing soft tissue sarcoma. Around 18 out of 100 tumours (18%) in people with Li Fraumeni syndrome are soft tissue sarcomas, most commonly rhabdomyosarcoma, leiomyosarcoma, liposarcoma and histiosarcoma.

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. Around 13 out of 100 children who have retinoblastoma (13%) develop a soft tissue sarcoma within 50 years.

The most common types are leiomyosarcoma, fibrosarcoma and rhabdomyosarcoma. The radiotherapy given as treatment for retinoblastoma may partly account for the increased risk. These children also have an increased risk of getting a type of bone cancer called osteosarcoma.

In the UK, Kaposi’s sarcoma is a very rare type of soft tissue sarcoma that develops from cells in the blood vessels. Kaposi's sarcoma is caused by Human Herpes Virus-8 infection (HHV-8), which is also known as Kaposi's sarcoma associated herpes virus (KSHV). Many people have HHV-8 and most do not develop Kaposis sarcoma. But this virus is sometimes able to cause Kaposi's sarcoma in people with lowered immunity.

HIV and AIDS cause lowered immunity and around 80 out of 100 people (80%) who get Kaposi's sarcoma have HIV or AIDS. People taking medicines to suppress their immunity (usually after an organ transplant) also have an increased risk of developing Kaposi’s sarcoma. 

An infection called Epstein Barr virus (EBV) has been linked with leiomyosarcomas in children and young people with HIV or AIDS. It's also been linked to leiomyosarcoma in adults taking medicines to lower immunity after a transplant. There are also a small number of reports of people developing angiosarcoma after kidney transplant.

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.

Less than 1 in every 3,000 women who have breast removal (mastectomy) and get chronic lymphoedema develop a type of sarcoma in the arm called angiosarcoma. This 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.

Children born with a hernia of the tummy button (a congenital umbilical hernia) or a hernia at the top of the leg (an inguinal hernia) are around 3 times more likely to have a Ewing’s sarcoma.

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.

One study found that women who are very overweight (obese) have a higher risk of sarcomas of the womb compared with women who are not overweight.

Possible risk factor

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 if the person has x-rays or scans.

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

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.

For detailed information on soft tissue sarcoma risks and causes

Information and help

Dangoor sponsorship

About Cancer generously supported by Dangoor Education since 2010.