SOFT TISSUE SARCOMAS
( By JASCAP )

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General

What are soft tissue sarcomas?

Soft tissue sarcomas are rare. About 2200 people a year in the UK will be diagnosed with a sarcoma.

Soft tissue sarcomas are cancers that develop from cells in the soft, supporting tissues of the body. They can occur in muscle, fat, blood vessels or in any of the other tissues that support, surround and protect the organs of the body. Soft tissue sarcomas can also develop in specific organs, such as the womb (uterus), stomach, skin and small bowel.

Some types of sarcoma occur in children, teenagers and young adults, but generally sarcomas are more likely to develop in people over the age of 30.

Almost half of all soft tissue sarcomas occur in the limbs – especially the legs. Other common sites are the chest, abdomen and pelvis. Less commonly they may occur in the head and neck.

Bone sarcomas

Some sarcomas, such as osteosarcomas, start in the bone. These grow and develop differently and are treated differently from soft tissue sarcomas. Occasionally it is hard to tell whether a sarcoma has started in soft tissue or bone. There are some types of sarcoma, such as Ewing’s tumours, that can begin in either bone or soft tissue.

We have a separate section on cancer that starts in the bone; primary bone cancer.

What is cancer?

The organs and tissues of the body are made up of tiny building blocks called cells. Cancer is a disease of these cells.

Cells in different parts of the body may look and work differently but most reproduce themselves in the same way. Cells are constantly becoming old and dying, and new cells are produced to replace them. Normally, cells divide in an orderly and controlled manner. If for some reason the process gets out of control, the cells carry on dividing, developing into a lump which is called a tumour.

Tumours can be either benign or malignant. Cancer is the name given to a malignant tumour. Doctors can tell if a tumour is benign or malignant by examining a small sample of cells under a microscope. This is called a biopsy.

In a benign tumour the cells do not spread to other parts of the body and so are not cancerous. However, if they continue to grow at the original site, they may cause a problem by pressing on the surrounding organs.

A malignant tumour consists of cancer cells that have the ability to spread beyond the original area. If the tumour is left untreated, it may spread into and destroy surrounding tissue. Sometimes cells break away from the original (primary) cancer. They may spread to other organs in the body through the bloodstream or lymphatic system.

The lymphatic system is part of the immune system - the body's natural defence against infection and disease. It is a complex system made up of organs, such as bone marrow, the thymus, the spleen, and lymph nodes. The lymph nodes (or glands) throughout the body are connected by a network of tiny lymphatic ducts.

When the cancer cells reach a new area they may go on dividing and form a new tumour. This is known as a secondary cancer or metastasis.

It is important to realise that cancer is not a single disease with a single type of treatment. There are more than 200 different kinds of cancer, each with its own name and treatment.

Types of cancer

Carcinomas

The majority of cancers, about 85% (85 in a 100), are carcinomas. They start in the epithelium, which is the covering (or lining) of organs and of the body (the skin). The common forms of breast, lung, prostate and bowel cancer are all carcinomas.

Carcinomas are named after the type of epithelial cell that they started in and the part of the body that is affected. There are four different types of epithelial cells:

squamous cells - that line different parts of the body, such as the mouth, gullet (oesophagus), and the airways
adeno cells - form the lining of all the glands in the body and can be found in organs such as the stomach, ovaries, kidneys and prostate
transitional cells - are only found in the lining of the bladder and parts of the urinary system
basal cells - that are found in one of the layers of the skin.

A cancer that starts in squamous cells is called a squamous cell carcinoma. A cancer that starts in glandular cells is called an adenocarcinoma. Cancers that start in transitional cells are transitional cell carcinomas, and those that start in basal cells are basal cell carcinomas.

Leukaemias and lymphomas

These occur in the tissues where white blood cells (which fight infection in the body) are formed, i.e. the bone marrow and lymphatic system. Leukaemia and lymphoma are quite rare and make up about 6.5% (6.5 in 100) of all cancers.

Sarcomas

Sarcomas are very rare. They are a group of cancers that form in the connective or supportive tissues of the body such as muscle, bone and fatty tissue. They account for less than 1% (1 in 100) of cancers.

Sarcomas are split into two main types:

bone sarcomas - that are found in the bones
soft tissue sarcomas - that develop in the other supportive tissues of the body.

Others forms of cancer

Brain tumours and other very rare forms of cancer make up the remainder of cancers.

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 below. Your doctor will be able to give you more details about which type of sarcoma you have. Each type of sarcoma is named after the type of cell from which it has grown, rather than the part of the body in which it started.

Fibrosarcomas
Myxofibrosarcomas
Desmoid tumours
Liposarcomas
Synovial sarcomas
Rhabdomyosarcomas
Leiomyosarcomas
Malignant peripheral nerve sheath tumours (MPNST)
Angiosarcomas
Gastrointestinal stromal tumours (GIST)
Kaposi's sarcoma (KS)
Other sarcomas
Ewing's tumours
Soft tissue sarcomas in children

Fibrosarcomas

These sarcomas start in cells called fibrocytes, which make up the fibrous tissues that join together the inner structures of the body: for example, muscles to bones.

They are most commonly found on the arms, legs or trunk, but can occur deeper in the body. Most people first notice them as a painless, firm lump.

Myxofibrosarcomas

This is a type of fibrous sarcoma and the most common type of sarcoma in older people. They were previously called malignant fibrous histiocytomas (MFH). It is not clear which type of cell they start from. Myxofibrosarcomas can affect any part of the body, but most commonly occur in the arms or legs.

Desmoid tumours

These tumours are another type of fibrous sarcoma. They are slow-growing and are sometimes said to be halfway between a fibrosarcoma and a benign fibroma (a non- cancerous tumour of fibrous tissue). Desmoid tumours do not 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 sarcomas.

Liposarcomas

These sarcomas start in the body’s fat cells. They can grow anywhere in the body and most commonly affect middle-aged people. Some grow very slowly (taking many years to develop) and others more quickly.

Synovial sarcomas

Synovial sarcomas usually start near to joints, such as the knee or elbow, but can occur in any part of the body. They usually appear as hard lumps and are more common in younger adults.

Rhabdomyosarcomas

Rhabdomyosarcomas grow in the active muscles of the body that we can control. These muscles are known as skeletal muscle or striated muscle. Rhabdomyosarcomas occur mostly in the head, neck and pelvis, but can occur in the arms or legs. There are three sub-types of rhabdomyosarcoma: embryonal, alveolar and pleomorphic.

Embryonal rhabdomyosarcomas tend to occur more commonly in children, while alveolar rhabdomyosarcomas occur more in the limbs of teenagers and young adults. Pleomorphic rhabdomyosarcoma tends to occur in middle-aged people.

Leiomyosarcomas

Leiomyosarcomas start from smooth muscle that is not under our conscious control. Smooth muscle is also called involuntary muscle and forms the walls of the womb, stomach, intestine and the blood vessels. Leiomyosarcoma is one of the more common types of sarcoma and can occur anywhere in the body.

Malignant peripheral nerve sheath tumours (MPNST)

These sarcomas arise in the cells that cover nerve cells and can occur anywhere in the body. The cells around the nerve cells are called schwann cells. MPNST can also be called malignant schwannomas or neurofibrosarcomas. They most commonly occur in people who have a rare genetic disorder called neurofibromatosis (von Recklinghausen’s disease).

Angiosarcomas

Angiosarcomas start from the cells that make up the walls of blood or lymph vessels. If they develop from blood vessels they are called haemangiosarcomas. If they start from the lymph vessels they are called lymphangiosarcomas. Angiosarcomas sometimes arise in a part of the body that has been treated with radiotherapy many years before.

Gastrointestinal stromal tumours (GIST)

GISTs are sarcomas that develop from the connective tissues in the walls of the digestive system. The digestive system is often called the gastrointestinal (GI) tract. This type of tumour may also be called GI stromal sarcoma. They 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. Coloured patches or lumps can develop in the skin, in the mouth, and in the 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 to other types of soft tissue sarcoma.

Other sarcomas

There are other, much rarer, types of sarcoma. These include:

alveolar soft part sarcoma
dermatofibrosarcoma protuberans (DFSP)
desmoplastic small round cell tumours
epithelioid sarcomas
extraskeletal myxoid chondrosarcomas
giant cell fibroblastoma (GCF).

Ewing's tumours

Ewing’s tumours are a type of bone sarcoma, but about a third of all Ewing’s tumours develop in the soft tissue and are known as extra-osseous Ewing’s tumours. Soft tissue Ewing’s sarcomas tend to behave differently to other soft tissue sarcomas and are usually treated in a similar way to bone sarcomas.

Soft tissue sarcomas in children

Soft tissue sarcomas also occur in children, particularly some types of rhabdomyosarcoma. Their symptoms and treatment may differ from those in an adult with the same sarcoma.

Our section on children's cancer discusses the treatment of children's cancers and includes information about some types of sarcoma that occur in children.

 
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