Learn about the different types of soft tissue sarcoma.
The type of soft tissue sarcoma you have tells you the type of cell that the cancer started in. Knowing this helps your doctor decide which treatment you need.
Leiomyosarcoma is the most common type of soft tissue sarcoma. In the UK around 600 cases are diagnosed every year.
Leiomyosarcomas develop from smooth muscle cells. This is the type of muscle that you do not control voluntarily. So it is called involuntary muscle.
It forms the walls of the womb, stomach, intestine and blood vessels. Rarely, leiomyosarcoma starts in the muscle of the womb and is called uterine sarcoma.
These are sarcomas that develop from fatty tissue and can grow anywhere in the body. They usually show up as soft lumps.
In the UK around 440 people are diagnosed with liposarcoma every year.
Fibroblastic sarcomas grow from cells in fibrous tissue. The cells are called histiocytes or fibrocytes. Fibrosarcomas can grow in any part of the body. They are commonly found in the arms or legs.
Around 460 cases of fibroblastic sarcoma are diagnosed in the UK every year.
There are different types of fibroblastic sarcoma:
Undifferentiated pleomorphic sarcoma
This type used to be called malignant fibrous histiocytoma (MFH). MFH used to be one of the most common types of soft tissue sarcoma. But doctors don't use this term very often now.
Most of the tumours that used to be called MFH are now more accurately diagnosed as other types of sarcoma. The small number that would still be called MFH are now known as undifferentiated pleomorphic sarcoma.
Dermatofibrosarcoma protuberans (DFSP)
It's extremely rare and starts in the skin. It occurs most often in adults in their 30s. It usually behaves like a non cancerous (benign) tumour and does not spread but in 2 to 5% of cases it can spread.
There is a small risk that DFSP can change and develop into a different type of fibrosarcoma which behaves more like a cancererous tumour. This is called malignant transformation.
This includes fibrosarcoma and myxofibrosarcoma.
Rhabdomyosarcomas develop from skeletal (striated) muscle cells. This is the type of muscle that you can control. Rhabdomyosarcomas can develop anywhere in the body.
In the UK around 120 people are diagnosed with rhabdomyosarcoma every year.
The main types of rhabdomyosarcoma include:
- Embryonal rhabdomyosarcomas - occurs more commonly in children and young people
- Alveolar rhabdomyosarcomas - occur more often in younger adults
- Pleomorphic rhabdomyosarcoma - this is rare and tends to occur in adults
Soft tissue Ewing's sarcomas
Ewing's sarcomas occur in bone and they can also develop and grow in soft tissues. Ewing's that grow in the soft tissue are called extra-skeletal Ewing's sarcoma. Extra-skeletal means they're outside the bone. Around 40 cases are diagnosed in the UK each year.
These soft tissue tumours behave a bit differently to other types of soft tissue sarcoma. They're usually treated in the same way as Ewing's sarcoma that start in the bone.
PNET stands for primitive neuroectodermal tumour. It used to describe a type of Ewing's sarcoma that starts in soft tissues. But doctors don't use this term any more.
All soft tissue Ewing's sarcomas are grouped together and described as extra-skeletal Ewing's sarcoma or soft tissue Ewing's sarcoma.
These sarcomas are most commonly found around the knee, and they start in cells close to joints and tendons. They can be found anywhere in the body. Around 80 cases are diagnosed in the UK each year.
These sarcomas usually show up as hard lumps but can be present for some time before they start to grow bigger. They're more common in young adults.
Vascular sarcomas develop from cells that make up the walls of blood or lymphatic vessels. Around 145 people are diagnosed with this in the UK every year.
There are different types of vascular sarcoma:
- Angiosarcomas - start from the cells that make up the walls of blood or lymphatic vessels
- Haemangiosarcomas - start in the blood vessels
- Lymphangiosarcomas - start in the lymph vessels
- Haemangioendothelioma - may start in soft tissues or in internal organs, such as the liver or lungs
Malignant peripheral nerve sheath tumours (MPNST)
These are cancers of the cells that cover nerves. In the UK around 80 people are diagnosed with nerve sheath tumours every year.
There are different types of MPNSTs including neurofibrosarcomas and malignant schwannomas. Schwannomas develop from the cells that form the fatty sheath which covers nerves. These cells are called schwann cells.
Gastrointestinal Stromal Tumours (GISTs)
Gastrointestinal stromal tumours can behave in a:
- non cancerous (benign) way - tends to be relatively slow growing and less likely to come back
- cancerous (malignant) way - is faster growing, and is more likely to come back or spread
You might hear GIST that behaves in a cancerous way called GI stromal sarcoma. Generally speaking, the larger the GIST, the more likely it is to behave like cancer.
These tumours develop from the cells of the connective tissues that support the organs of the digestive system – the gastrointestinal tract. Most are found in the stomach. GIST is treated differently from other types of soft tissue sarcoma.
Angiosarcoma of the heart
Tumours that affect the heart are very rare. Most tumours that start in the heart are not cancer, they are benign. About 1 in 4 (25%) are cancers. Most commonly these are soft tissue sarcomas.
Angiosarcomas are a type of soft tissue sarcoma that grow from cells that make up the walls of blood vessels.
The main treatment for angiosarcoma of the heart is surgery to completely remove the cancer. Other treatments include chemotherapy and radiotherapy.
Kaposi’s sarcoma develops from cells called endothelial cells. Most cases occur in the skin but it can also develop in internal organs of the body. It's very rare, with only around 150 cases diagnosed in the UK each year.
Some types of Kaposi's sarcoma are known to be associated with HIV (human immunodeficiency virus) infection and AIDS (acquired immunodeficiency syndrome). It can be caused by a sexually transmitted virus called human herpes virus 8 (HHV8) or Kaposi's sarcoma herpes virus (KSHV). Other types are associated with Jewish, Italian and West African ancestry.
Kaposi's sarcoma is treated differently to many soft tissue sarcomas.
Fibromatosis is not actually a sarcoma, but we have included it here because we are sometimes asked about it. Fibromatosis is not cancer. It does not spread around the body but these tumours can spread into nearby tissues. It is also called aggressive fibromatosis or a desmoid tumour.