Types of soft tissue sarcoma

Soft tissue sarcoma is a cancerous (malignant) tumour that starts in the soft tissues of the body, which include fat, muscle, fibrous tissue, blood vessels, lymph vessels and nerves. Soft tissue sarcoma can grow into nearby tissue and destroy it. It can also spread (metastasize) to other parts of the body.

There are more than 50 types of soft tissue sarcoma. They are grouped by the type of soft tissue where the tumour started.

A soft tissue sarcoma that starts in the fat tissue (adipose) of the body is called a liposarcoma. It is one of the most common types of soft tissue sarcoma in adults. It makes up about 20% of all soft tissue sarcomas in adults.

Liposarcoma usually develops in adults between 50 and 65 years old. It most often starts in the fat tissue behind the knee, in the thigh or at the back of the abdomen (retroperitoneum). It can grow slowly or quickly.

There are different types of liposarcoma. They are named based on how the fat cells look under a microscope. The types of liposarcoma are:

• well-differentiated liposarcoma or atypical lipomatous tumour
• dedifferentiated liposarcoma
• myxoid liposarcoma
• pleomorphic liposarcoma

A soft tissue sarcoma can start in fibrous tissue that joins together parts inside the body. This group (sometimes called fibroblastic and myofibroblastic sarcomas) includes many different types.

The following are some soft tissue sarcomas of fibrous tissue.

Myxofibrosarcoma is one of the most common types of soft tissue sarcoma that commonly develops in adults around 60 years or older. It most often starts in the fibrous tissue of the legs or arms. Myxofibrosarcomas tend to grow slowly. They often come back (recur) after they are removed and may change into a fast-growing cancer that is more likely to spread to other parts of the body, such as the lungs or bone.

Fibrosarcoma( also called adult fibrosarcoma) is an uncommon type of soft tissue sarcoma that usually develops in middle-aged to older adults. It is made up of cells called fibroblasts and collagen (a protein found in fibrous tissues that gives the body strength and cushioning). It most often starts in deep fibrous tissue of an arm or leg, the trunk of the body or the head and neck area. Sometimes a fibrosarcoma starts in tissue that has been treated with radiation therapy.

Dermatofibrosarcoma protuberans is a rare type of soft tissue sarcoma in the fibrous tissue of the skin. It usually develops in young adults around 30 years old. Dermatofibrosarcoma protuberans tends to grow slowly and often starts in the trunk of the body, an arm or a leg. It develops in the thick, middle layer of the skin (dermis). It tends to spread along the skin and may grow into deeper tissues, but it doesn’t usually spread to other parts of the body. Surgery is usually done to remove the cancer along with some normal tissue around it (called a wide local excision).

Solitary fibrous tumour used to be called hemangiopericytoma. It is made up of tightly packed cells that surround vessels. Solitary fibrous tumours are most common in middle-aged adults and often start in the legs, arms or pelvis. Most solitary fibrous tumours grow slowly.

A soft tissue sarcoma can start in the muscle tissue of the body. There are 3 types of muscle tissue – smooth muscle, skeletal muscle and cardiac (heart) muscle.

Leiomyosarcoma is one of the most common types of soft tissue sarcoma and usually develops in middle-aged or older adults. It starts in the smooth muscle. The smooth muscle works automatically without you thinking about it (involuntary muscle). Leiomyosarcomas can develop almost anywhere in the body, but they most often form in digestive organs like the stomach or in large blood vessels. Leiomyosarcoma can also develop in the wall of the uterus (called uterine sarcoma) .

Rhabdomyosarcoma is the most common type of soft tissue sarcoma in children. It rarely happens in adults. Rhabdomyosarcoma starts in skeletal muscle, which is a type of muscle that you control to move your body (voluntary muscle). It most often starts in the head and neck area, arms, legs and trunk of the body. Find out more about rhabdomyosarcoma.

A soft tissue sarcoma can start in the walls of blood vessels or lymph vessels. These are sometimes called vascular sarcomas.

Angiosarcoma usually starts in the vessels in the skin or other tissues close to the surface of the body.

It can also develop in the liver, breast, wall of the abdomen or heart. Many angiosarcomas develop in an area where there is a buildup of lymph fluid( called lymphedema), or where radiation therapy was given or where both have happened. They tend to come back after treatment.

Epithelioid hemangioendothelioma starts in the epithelial cells that line the blood vessels. It may develop anywhere in the body, but mostly affects the liver or the lungs. These soft tissue sarcomas tend to grow slowly. They are considered less aggressive, but they may grow into nearby tissues and can sometimes spread to other parts of the body.

Kaposi sarcoma is an uncommon tumour that also develops in the blood vessels. Find out more about Kaposi sarcoma.

A soft tissue sarcoma can start in the nerve tissue outside of the brain and spinal cord (called the peripheral nervous system).

Malignant peripheral nerve sheath tumours (MPNSTs) start in the cells that cover nerves. They can develop anywhere in the body, but they most often affect major nerves at the back of the abdomen and in the legs. MPNSTs grow quickly. They tend to come back after treatment and are more likely to spread to other parts of the body. People with neurofibromatosis type 1 have a higher risk of developing an MPNST.

Malignant granular cell tumour is a rare soft tissue sarcoma that is thought to develop in nerve tissue. It usually forms just under the skin (subcutaneous) and is most often found in the mouth, pancreas and bile duct. These tumours can happen in many places at the same time.

A soft tissue sarcoma can start in the soft tissue outside the bone and around it. This soft tissue is made up of bone tissue that has not hardened (osteoid) and cartilage. Extraskeletal tumours may also be called extraskeletal chondro-osseous tumours.

Extraskeletal osteosarcoma is also called extraosseous osteogenic sarcoma. It is a very rare tumour that develops in the soft tissues around the bone, but not in or on the bone itself. Most extraskeletal osteosarcomas happen in the arm or leg. They can also develop in the breast, chest wall, back of the abdomen (retroperitoneum), bladder or other internal organs. Most of these tumours are high grade, which means they grow quickly and can spread to other parts of the body.

Extraskeletal chondrosarcoma is a rare type of soft tissue sarcoma. It often starts in the soft tissues of the upper arms or hands. It can also start around limb girdles, where the long bones attach to the trunk of the body. These tumours happen most often in people older than 35 years of age. They are almost twice as common in males as in females.

A soft tissue sarcoma can start in the connective tissues that support the gastrointestinal (GI) tract. It can develop anywhere along the GI tract. Most GISTs start in the stomach.

Find out more about gastrointestinal stromal tumours (GISTs).

Some soft tissue sarcomas are made up of cells that do not look like any specific type of soft tissue, so it is difficult to tell where the cancer started. These tumours are called uncertain tissue tumours or tumours of uncertain differentiation.

Alveolar soft part sarcoma is a rare tumour. It usually happens in young adults and affects women more often than men. This type of tumour most commonly develops in the legs. It grows slowly, but it is known to spread to the lungs, brain or bone in the early stages.

Clear cell sarcoma grows slowly and usually develops in the tendons of young adults. It is like melanoma and the cells contain melanin, which is the substance that gives skin its colour. Clear cell sarcoma tends to spread to nearby lymph nodes.

Soft tissue Ewing sarcoma is also called extraskeletal Ewing sarcoma. Ewing sarcoma usually develops in the bone, but soft tissue Ewing sarcoma starts in soft tissues around bones. It usually happens in the trunk of the body, legs and arms and in the head and neck area. Soft tissue Ewing sarcoma is different than other soft tissue sarcomas. The cells of these tumours look and act very much like Ewing sarcoma of the bone, so they are usually treated like Ewing sarcoma of the bone.

Synovial sarcoma most often starts in the tissue around the joints of the knee or ankle. It can also start in the hip or shoulder. Synovial sarcoma tends to grow slowly and usually develops in young adults. Although they are named synovial sarcomas, these tumours don’t start in the tissue that lines the joints (synovial tissue). They can be found in areas of the body not around synovial tissue, such as the head and neck area. For this reason, they are classified as uncertain tissue tumours.

These are other types of uncertain tissue tumours:

• desmoplastic small round cell tumour
• epithelioid sarcoma
• extraskeletal myxoid chondrosarcoma
• perivascular epithelioid cell tumour (PEComa)

A soft tissue sarcoma can start in tissues that are made up of undifferentiated cells. This means that the cancer cells don’t look like normal cells and are arranged very differently. They tend to grow very quickly and are likely to spread. Undifferentiated tumours can’t be classified into any other group of soft tissue sarcomas.

Undifferentiated pleomorphic sarcoma used to be called malignant fibrous histiocytoma. But now doctors are better able to diagnose malignant fibrous histiocytomas as other types of soft tissue sarcoma. Undifferentiated pleomorphic sarcoma is usually found in the arms and legs. It may also develop in the back of the abdomen.

Other undifferentiated tumours include:

• undifferentiated spindle cell sarcoma
• undifferentiated round cell sarcoma
• undifferentiated epithelioid sarcoma