Soft Tissue Sarcomas

About soft tissue sarcomas

Cancer starts when cells start to grow out of control. Cells in nearly any part of the body can become cancer and spread to other areas. To learn more about how cancers start and spread, see What Is Cancer?.

There are many types of soft tissue tumors, and not all of them are cancerous. Many benign tumors are found in soft tissues. A benign tumor is not cancer. It typically can't spread to other parts of the body.

Some soft tissue tumors have traits of both cancers and benign tumors. These are called intermediate soft tissue tumors.

Sarcomas are an uncommon type of cancer that start from bone or soft tissues, like muscle, fat, nerves, fibrous tissue, or blood vessels. Bone and soft tissue sarcomas are the main types of sarcomas.

Soft tissue sarcomas can be found in any part of the body. Most of them start in the arms or legs. They can also be found in the trunk, head and neck area, internal organs, and the area behind the abdominal cavity, known as the retroperitoneum.

Sarcomas that most often start in bones, such as osteosarcomas, and sarcomas that are most often seen in children, such as the Ewing family of tumors and rhabdomyosarcomas, are not covered here.

Types of soft tissue sarcomas

There are more than 50 different types of soft tissue sarcomas. Some are quite rare, and not all are listed here.

Adult fibrosarcoma usually starts in the fibrous (connective) tissue of the legs, arms, or trunk. It is most common in adults between the ages of 20 and 60 but can occur in people of any age, even in infants. However, infantile fibrosarcoma is a different, usually less aggressive type.

Alveolar soft-part sarcoma is rare and mostly affects young adults. It most often begins in the deep soft tissue of the legs.

Angiosarcoma starts in blood vessels (hemangiosarcomas) or in lymph vessels (lymphangiosarcomas). These tumors sometimes start in a part of the body that has been treated with radiation. Angiosarcomas are sometimes seen in the breast after radiation therapy or in limbs with chronic swelling (lymphedema).

Clear cell sarcoma is a rare cancer that often starts in the tendons of the arms or legs. Under the microscope, it looks a lot like melanoma, a type of skin cancer. How cancers with these features start in parts of the body other than the skin is not known.

Desmoplastic small round cell tumor is a rare and aggressive cancer seen mostly in teens and young adults, often in males.  It's found most often in the abdomen.

Epithelioid sarcoma most often starts in tissues under the skin of the hands, forearms, feet, or lower legs. It often affects teens and young adults.  There is also a “proximal” subtype that starts closer to the center of the body, like the pelvis or trunk. 

Fibromyxoid sarcoma, low-grade grows slowly and often appears as a painless growth on the trunk or arms or legs, particularly the thigh. It is more common in young to middle-aged adults and is sometimes called an Evans’ tumor.

Gastrointestinal stromal tumor (GIST) is a type of sarcoma that starts in the digestive tract. See Gastrointestinal Stromal Tumor (GIST) for more details.

Kaposi sarcoma starts in the cells that line blood or lymph vessels.  It is linked to infection with a virus called human herpesvirus 8 (HHV-8).  See Kaposi Sarcoma for more details.

Leiomyosarcoma is a type of cancer that starts in smooth muscle tissue. These tumors often start in the abdomen or uterus, but they can also start in the arms or legs. See Uterine Sarcoma for more details.

Liposarcoma is a cancer of fat tissue. It can start anywhere in the body but is most common in the thigh and deep inside the abdomen. It mainly affects adults, often between 50 and 65 years old.

Malignant mesenchymoma is a rare cancer that shows features of fibrosarcoma along with at least two other types of sarcoma in the same tumor. Many of these tumors are classified by their dominant type under newer pathology naming systems.

Malignant peripheral nerve sheath tumors start in cells that surround nerves. Types include neurofibrosarcomas, malignant schwannomas, and neurogenic sarcomas. They are often seen in people with a condition called neurofibromatosis type 1 (NF1).

Myxofibrosarcoma is most often found in older adults. It usually starts in the arms or legs, just under the skin, and there can sometimes be more than 1 tumor in the same area. 

Synovial sarcoma starts in the tissues around joints, most often the hip, knee, ankle, or shoulder. It is more common in children and young adults but can occur at any age.

Undifferentiated pleomorphic sarcoma (UPS), once called malignant fibrous histiocytoma (MFH), most often starts in the arms or legs and sometimes deep in the back of the abdomen (the retroperitoneum). It is a high-grade, fast-growing sarcoma that is most common in older adults and can spread to other parts of the body, especially the lungs.

Intermediate soft tissue tumors

These tumors might grow and invade nearby tissues and organs, but they do not tend to spread to other parts of the body.

Dermatofibrosarcoma protuberans (DFSP) is a slow-growing tumor that starts in the deeper layers of the skin. It usually appears on the chest, back, belly, arms, or legs. It tends to grow into nearby tissues but rarely spreads to distant sites.

Desmoid-type fibromatosis (fibromatosis/ desmoid tumor) is a tumor made of fibrous tissue with features in between fibrosarcoma and benign tumors such as fibromas (see below). They tend to grow slowly but often steadily. They do not spread to distant parts of the body, but they can cause serious problems by growing into nearby tissues. Some doctors consider them a type of low-grade fibrosarcoma, but others believe they are a unique type of fibrous tissue tumor. Certain hormones, like estrogen, make some desmoid tumors grow.

Epithelioid hemangioendothelioma is a blood vessel tumor that is considered a low-grade cancer, meaning it grows slowly and is slow to spread. It does grow into nearby tissues and sometimes can spread to distant parts of the body. It might start in soft tissues or in internal organs, such as the liver or lungs.

Infantile fibrosarcoma is the most common soft tissue sarcoma in children under 1 year of age. It tends to be slow-growing and is less likely to spread to other organs than adult fibrosarcomas. Many infantile fibrosarcomas have a gene change involving the NTRK gene. Some can be treated with targeted therapy if surgery or chemotherapy is not enough. 

Solitary fibrous tumors are most often benign, but some are cancer (malignant). Some start in the thigh, underarm, brain, or pelvis. They can also start in the tissue lining the lungs, called the pleura. Many tumors that were once called hemangiopericytomas are now considered solitary fibrous tumors.

Benign soft tissue tumors

Many benign tumors can start in soft tissues. These include:

Elastofibromas are benign tumors made of fibrous tissue. They often are found under the shoulder blade in older adults. 

Fibromas are benign tumors made of fibrous tissue. They grow slowly and do not spread. 

Fibrous histiocytomas are benign tumors made of fibrous tissue found in the skin or soft tissues. 

Glomus tumors are benign tumors that grow from cells found around blood vessels. They often occur under the fingernails and can be painful. 

Granular cell tumors are usually benign tumors that often start in the tongue but can be found almost anywhere in the body.

Hemangiomas are very common benign tumors of blood vessels. They often are found in infants and usually shrink or fade with time. 

Hibernomas are rare benign tumors made of brown fat tissue, a type of fat involved in heat production. 

Lipomas are very common benign tumors of fat tissue. They are soft, movable, and usually painless.

Leiomyomas are benign tumors of smooth muscle that can be found anywhere in the body. They are very common in the walls of the uterus, where they are known as fibroids.

Lipoblastomas are benign fat tissue tumors most often seen in children.

Lymphangiomas are benign tumors of lymph vessels. They often appear in infants and young children and can grow in the head, neck, or armpit. 

Myxomas are benign tumors that usually occur in muscles but do not come from muscle cells.

Neurofibromas are usually benign tumors that form from nerve tissue. They are very common in people with neurofibromatosis type 1 (NF1). Neurofibromas on large nerves, such as in the neck or upper arm, have a small risk of becoming cancerous. 

Neuromas are benign tumors of nerves. They can cause pain, tingling, or sensitivity in the affected area.

PEComas are a group of tumors made up of abnormal cells called perivascular epithelial cells. Although most of these tumors are benign, some rare PEComas are cancerous. The most common types of PEComas are angiomyolipomas, usually in the kidney, and lymphangioleiomyomas (LAM), a rare disease in women where tumor cells grow in the lungs and cause breathing problems.

Rhabdomyomas are benign tumors made of skeletal and heart muscle.

Schwannomas (neurilemmomas) are benign tumors that grow from Schwann cells, cells that coat and protect nerves. They tend to be slow-growing. 

Tenosynovial giant cell tumors (TGCT) are benign tumors that grow in or around joints and tendon sheaths. They often affect the fingers, knees, or feet and cause swelling or stiffness. The diffuse type TGCT is called pigmented villonodular synovitis (PVNS). The localized type TGCT is called nodular tenosynovitis.

Spindle cell tumors

Spindle cell tumors and spindle cell sarcomas are descriptive names used when tumor cells look long and narrow under the microscope. Spindle cell tumor is not a specific diagnosis or a specific type of cancer.

The tumor might be a sarcoma or sarcomatoid – meaning that it’s another type of tumor that looks like a sarcoma under the microscope.

Tumor-like conditions of soft tissue

Some changes in soft tissues are caused by inflammation or injury and can form a mass that looks like a soft tissue tumor. Unlike a real tumor, they don't come from a single abnormal cell, they have limited ability to grow or spread to nearby tissues, and they never spread to other parts of the body.

Nodular fasciitis and myositis ossificans are 2 examples. They affect tissues under the skin and muscle tissues, respectively.