What is a soft tissue sarcoma?
A sarcoma is a type of cancer that develops from certain tissues, like bone or muscle. There are 2 main types of sarcoma: bone sarcomas and soft tissue sarcomas. Soft tissue sarcomas can develop from soft tissues like fat, muscle, nerves, fibrous tissues, blood vessels, or deep skin tissues. They can be found in any part of the body. Most of them develop in the arms or legs. They can also be found in the trunk, head and neck area, internal organs, and the area in back of the abdominal cavity (known as the retroperitoneum). Sarcomas are not common tumors, and most cancers are the type of tumors called carcinomas.
There are many types of soft tissue tumors, and not all of them are cancerous. When a tumor is not cancerous, it is called benign. When the term sarcoma is part of the name of a disease, it means the tumor is malignant (cancer). There are about 50 different types of soft tissue sarcomas (not all are listed here).
This document is about soft tissue sarcomas in adults. Sarcomas occurring in bone, such as osteosarcomas and Ewing Family of Tumors are discussed in separate documents. Rhabdomyosarcoma, the most common type of soft tissue sarcoma seen in children, is also discussed in another document.
Fat tissue tumors
Benign fat tissue tumors
Lipomas are benign tumors of fat tissue. They are the most common benign soft tissue tumor. Most are found just under the skin, but they can develop anywhere in the body.
Lipoblastomas are benign fat tumors that occur in infants and young children.
Hibernomas, like lipomas, are also benign fat tissue tumors. They are much less common than lipomas.
Cancerous fat tissue tumors
Liposarcomas are malignant tumors of fat tissue. They can develop anywhere in the body, but they most often develop in the thigh, behind the knee, and inside the back of the abdomen. They occur mostly in adults between 50 and 65 years old.
Muscle tissue tumors
There are 2 types of muscle: smooth and skeletal.
Smooth muscle is found in internal organs such as stomach, intestines, blood vessels, or uterus (womb) and causes them to contract. These muscles are involuntary — we don’t control their movement.
Skeletal muscle is sometimes called striated (because stripes can be seen inside the cells under the microscope). This is the type of muscle that lets us move our arms and legs and other body parts when we want them to move— this is called voluntary movement.
Benign muscle tumors
Leiomyomas are benign tumors of smooth muscle. Leiomyomas can start from the walls of blood vessels, so they can develop almost anywhere in the body. They can be found in both men and women, but the most common place to find a leiomyoma is in the walls of the uterus. They are often called fibroids.
Rhabdomyomas are rare benign tumors of skeletal muscle.
Malignant muscle tumors
Leiomyosarcomas are malignant tumors of smooth muscle. Like leiomyomas, they can grow almost anywhere in the body. They are most often found in the retroperitoneum (area in back of the abdominal cavity), the internal organs, and blood vessels. These tumors are less often found in the deep soft tissues of the legs or arms. They tend to occur in adults, particularly the elderly. Leiomyosarcomas of the uterus are discussed in detail in our document, Uterine Sarcoma.
Rhabdomyosarcomas are malignant tumors of skeletal muscle. These tumors commonly grow in the arms or legs, but they can also begin in the head and neck area and in reproductive and urinary organs like the vagina or bladder. Children are affected much more often than adults. For more information, see our document, Rhabdomyosarcoma.
Peripheral nerve tissue tumors
The brain and spinal cord are parts of the central nervous system. The nerves that run throughout the body are part of the peripheral nervous system. Tumors can start in these peripheral nerves.
Benign nerve tumors
Neurofibromas, schwannomas (neurilemmomas), and neuromas are all benign tumors of nerves. These tumors can occur almost anywhere in the body. Neurofibromas are very common in people with an inherited condition called neurofibromatosis (also called von Recklinghausen disease). Sometimes neurofibromas of very large nerves (like those in the upper arms or neck) can become malignant.
Malignant nerve tumors
Neurofibrosarcomas, malignant schwannomas, and neurogenic sarcomas are malignant tumors of the cells that surround a nerve. These are also called malignant peripheral nerve sheath tumors.
Gastrointestinal stromal tumor (GIST) is a type of sarcoma that develops in the digestive tract. It starts in the cells that control the muscles lining the stomach and intestine. These muscles propel food through the digestive tract. GISTs are not discussed further in this document, but are covered in detail in our document, Gastrointestinal Stromal Tumor (GIST).
Joint tissue tumors
Our joints are surrounded by a capsule made of a tough tissue called synovium. This tissue produces a fluid that lubricates the joint surfaces so that they move smoothly. Joint tissue tumors can start in the synovium.
Benign joint tumors
Nodular tenosynovitis is a benign tumor of joint tissue. It is most common in the hands and is more common in women than in men.
Malignant joint tumors
Synovial sarcoma is a malignant tumor of the tissue around joints. The most common locations are the knee and ankle. Other sites are the shoulder and hip. This tumor is more common in children and young adults, but it can occur in older people.
Blood and lymph vessels tumors
Benign vessel tumors
Hemangiomas are benign tumors of blood vessels. They are rather common and can affect the skin or internal organs. They are sometimes present at birth, and some disappear without treatment.
Lymphangiomas are benign lymph vessel tumors that are usually present at birth. Lymph is a fluid that circulates in every tissue of the body, ending up in the venous system. It carries waste products from tissues and immune system cells.
Glomus tumors are benign tumors that are found around blood vessels (perivascular). They usually are found under the skin of the fingers.
Intermediate vessel tumors
Hemangiopericytoma is another tumor of perivascular tissue. This tumor can be either benign or malignant. It most often starts in the legs, pelvis, and retroperitoneum (the back of the abdominal cavity). It is most common in adults. This type of tumor usually doesn't spread to distant sites, but it does tend to come back in or near the same place that it started, even if it was removed completely at surgery.
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 (metastasize). It may start in soft tissues or in internal organs, such as the liver or lungs.
Malignant vessel tumors
Angiosarcoma is a malignant tumor that can develop either from blood vessels (hemangiosarcomas) or from lymph vessels (lymphangiosarcomas). These tumors are linked to radiation exposure — they sometimes start in a part of the body that has been treated with radiation. Angiosarcomas are sometimes seen in the breast after radiation therapy for breast cancer, and in limbs that are chronically swollen because lymph circulation is blocked (lymphedema).
Kaposi sarcoma is a cancer formed by cells similar to those lining blood or lymph vessels. In the past, Kaposi sarcoma was an uncommon cancer mostly seen in older people who had no apparent immune system problems. But it is now seen more often in people with suppressed immune systems (from HIV infection and organ transplants). It is not discussed further in this document, but is covered in detail in our document, Kaposi Sarcoma.
Fibrous tissue tumors
Fibrous tissue forms tendons and ligaments and covers bones as well as other organs in the body.
Benign fibrous tumors
- Superficial fibromatosis
- Fibrous histiocytomas
Intermediate fibrous tumors
Fibromatosis is the name given to fibrous tissue tumor with features in between fibrosarcoma and benign tumors such as fibromas and superficial fibromatosis. They tend to grow slowly but, often, steadily. These tumors are also called desmoid tumors, as well as the more scientific name musculoaponeurotic fibromatosis. They do not spread to distant sites, but they do cause problems by growing into nearby tissues. They can sometimes be fatal. Some doctors consider them a type of low-grade fibrosarcoma; but others believe they are a unique type of fibrous tissue tumors. Certain hormones, particularly estrogen, make some desmoid tumors grow. Anti-estrogen drugs are sometimes useful in treating desmoids that cannot be completely removed by surgery.
Dermatofibrosarcoma protuberans is a slow-growing cancer of the fibrous tissue beneath the skin, usually in the trunk or limbs. It grows into nearby tissues but rarely spreads to distant sites.
Malignant fibrous tumors
Fibrosarcoma is cancer of fibrous tissue. It usually affects the legs, arms, or trunk. It is most common in people between the ages of 20 and 60, but can occur at any age, even in infancy.
Uncertain tissue type tumors
Doctors look at tumor tissue under the microscope and do other tests and can usually find similarities between most sarcomas and certain types of normal soft tissues. But some sarcomas have not been linked to a specific type of normal soft tissue.
Benign uncertain tissue type tumors
Myxoma is a benign tumor that usually is located in muscles but does not start from muscle cells. The cells of a myxoma produce mucus-like material, a feature that distinguishes this tumor. It almost always occurs in adults.
Granular cell tumors are usually benign tumors in adults that occur often in the tongue but can be found almost anywhere in the body.
PEComa is a family of tumors made up of abnormal cells called perivascular epithelial cells. Although most of these tumors are benign, some rare PEComas are malignant (cancer). The most common PEComas are angiomyolipoma and lymphangioleiomyomatosis (LAM). Angiomyolipoma is a benign tumor that most often affects the kidney. LAM is a disease of women in which the tumor cells grow into the lung tissue and interfere with lung function.
Malignant uncertain tissue type tumors
Malignant mesenchymoma is a rare type of sarcoma that has some areas showing features of fibrosarcoma and other areas with features of at least 2 other types of sarcoma.
Alveolar soft-part sarcoma is a rare cancer that mostly affects young adults. These tumors most commonly occur in legs.
Epithelioid sarcoma most often develops in tissues under the skin of the hands, forearms, feet, or lower legs. Adolescents and young adults are often affected.
Clear cell sarcoma is a rare cancer that often develops in tendons of the arms or legs. Under the microscope, it has some features of malignant melanoma, a type of cancer that develops from pigment-producing skin cells. 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 sarcoma of adolescents and young adults, found most often in the abdomen. Its name means that it is formed by small, round cancer cells surrounded by scar-like tissue.
Pleomorphic undifferentiated sarcoma, also known as malignant fibrous histiocytoma (MFH), is most often found in the arms or legs. Less often, it can start inside the back of the abdomen. This sarcoma is most common in older adults. Although it mostly tends to grow locally, it can spread to distant sites.
Spindle cell tumor and spindle cell sarcoma are named based on the long, narrow appearance of the cells under the microscope). A spindle cell tumor is a tumor with cells that look like these. Spindle cell tumor is not a specific diagnosis or a specific type of cancer. The tumor may be a sarcoma, or it can be sarcomatoid — meaning another type of tumor (like a carcinoma) that looks like a sarcoma under the microscope.
Other types of sarcoma
There are other types of tumors called soft tissue sarcomas, but these are all quite rare.
Tumor-like conditions of soft tissue
Some conditions of soft tissues are caused by inflammation or injury and can form a mass that looks like a soft tissue tumor. Unlike a true tumor, they do not come from a single abnormal cell, they have limited capacity to grow or spread to nearby tissues, and never spread through the bloodstream or lymph system. Nodular fasciitis and myositis ossificans are 2 examples which affect tissues under the skin and muscle tissues, respectively.
Last Medical Review: 10/21/2013
Last Revised: 02/06/2014