Soft tissue sarcoma is a rare type of cancer that starts as a growth of cells in the body's soft tissues. The soft tissues connect, support and surround other body structures. Soft tissues include muscle, fat, blood vessels, nerves, tendons and linings of the joints.

Soft tissue sarcoma can happen anywhere in the body. It happens most often in the arms, legs and belly.

More than 50 types of soft tissue sarcoma exist. Some types are more likely to affect children. Others affect mostly adults. These cancers can be hard to diagnose because they may be mistaken for many other types of growths.

Soft tissue sarcoma treatment usually involves surgery. Other treatments might include radiation therapy and chemotherapy. Treatment depends on the size, type and location of the cancer and how quickly it grows.


A soft tissue sarcoma may not cause any symptoms at first. As the cancer grows, it may cause:

  • A noticeable lump or swelling.
  • Pain, if the growth presses on nerves or muscles.

When to see a doctor

Make an appointment with your health care team if you have any symptoms that worry you.


It's not clear what causes most soft tissue sarcomas.

Soft tissue sarcoma starts when a connective tissue cell gets changes in its DNA. A cell's DNA holds the instructions that tell a cell what to do. The changes turn the connective tissue cells into cancer cells. The changes tell the cancer cells to grow and make more cells. Healthy cells die as part of their natural cycle, but cancer cells keep growing because they do not have instructions to stop.

The cancer cells form a growth, called a tumor. In some types of soft tissue sarcoma, the cancer cells stay in one location. They continue making more cells and cause the tumor to get bigger. In other types of soft tissue sarcoma, the cancer cells might break away and spread to other parts of the body.

The type of cell with DNA changes is what determines the type of soft tissue sarcoma. For example, angiosarcoma begins in cells in the lining of blood vessels, while liposarcoma starts in fat cells.

Some types of soft tissue sarcoma include:

  • Angiosarcoma.
  • Dermatofibrosarcoma protuberans.
  • Epithelioid sarcoma.
  • Gastrointestinal stromal tumor (GIST).
  • Kaposi's sarcoma.
  • Leiomyosarcoma.
  • Liposarcoma.
  • Malignant peripheral nerve sheath tumor.
  • Myxofibrosarcoma.
  • Rhabdomyosarcoma.
  • Solitary fibrous tumor.
  • Synovial sarcoma.
  • Undifferentiated pleomorphic sarcoma.

Risk factors

Factors that may raise the risk of sarcoma include:

  • Inherited syndromes. A risk of soft tissue sarcoma can run in families. Genetic syndromes that increase the risk include hereditary retinoblastoma, Li-Fraumeni syndrome, familial adenomatous polyposis, neurofibromatosis, tuberous sclerosis and Werner syndrome.
  • Chemical exposure. Being exposed to certain chemicals may increase the risk of soft tissue sarcomas. These chemicals include herbicides, arsenic and dioxin.
  • Radiation exposure. Radiation therapy for other cancers can increase the risk of soft tissue sarcomas.