Soft Tissue Sarcomas

What are soft tissue sarcomas?

Soft tissue sarcomas are malignant tumors that begin in soft tissue, such as muscle, fibrous tissues, tendons, fat, nerves, joint tissues and blood vessels.

These tumors are rare and can form anywhere in the body. Usually, fewer than 1,000 new soft tissue sarcomas are reported in children each year in the United States.

Often painless, soft tissue sarcomas can be present and grow in the body for a long period of time before they are discovered. Most children notice a rapidly enlarging mass (over several weeks or months) and pain when the mass is touched.

There are several types of soft tissue sarcomas. The most common include:

  • Rhabdomyosarcoma — a tumor of skeletal muscles and the most common soft tissue sarcoma in children
  • Non-rhabdomyosarcomas, including but not limited to:

o   Infantile fibrosarcoma — a tumor found in the tissue that forms tendons and ligaments; this is most common soft tissue sarcoma in babies up to 1 year old, and is often present at birth.

o   Malignant peripheral nerve sheath tumor — a tumor found in cells that surround nerves and is more common in patients with neurofibromatosis type 1.

o   Synovial sarcoma — a tumor found in tissue near joints, usually the knee or ankle, also seen in the foot.

Causes of soft tissue sarcomas

Most soft tissue sarcomas are characterized by genetic changes that occur after birth in the tumor cells. There are many different genetic changes that occur in soft tissue sarcomas, and these can be detected by testing the tumor. The result of these changes is uncontrolled cell growth and cancer formation.

Most of the genetic changes associated with soft tissue sarcomas occur only in the tumor cells and cannot be passed on from parent to child. However, in rare cases, an increased risk of soft tissue sarcoma has been linked to genetic mutations that are inherited, such as Li-Fraumeni syndrome or neurofibromatosis.

Signs and symptoms of soft tissues sarcomas

Symptoms of soft tissue sarcomas can include:

  • Painless or painful swelling or a lump
  • Pain or weakness due to the tumor compressing nerves or muscles
  • A limp, if the tumor is located on the leg or foot 

Testing and diagnosis soft tissue sarcomas

Symptoms of soft tissue sarcomas can be difficult to identify in children, so prompt evaluation of any lump or mass is important.

Diagnosing a soft tissue sarcoma begins with a complete medical history and physical examination of your child. A detailed neurological assessment may also be performed.

At Children’s Hospital of Philadelphia (CHOP), clinicians use a variety of diagnostic tests to correctly diagnose soft tissue tumors, including:

  • Magnetic resonance imaging (MRI), which uses a combination of large magnets, radiofrequencies and a computer to produce detailed images of organs, soft tissues, muscles, ligaments and other structures within the body. Your child is exposed to no radiation during an MRI.
  • Ultrasound, which uses sound waves to produce images of the organs and soft tissues inside the body. The images are viewed live and continually on a computer screen and can help detect any anomalies.
  • X-rays, which produce images of bones.
  • Positron emission tomography (PET) scan, which uses radioactive sugar injected into a vein and a scanner to make detailed, computerized pictures of areas of the body.
  • Needle biopsy, which is a procedure where a doctor places a small needle through the skin and into the lesion to withdraw a small sample of the abnormal tissue. The tissue is analyzed to confirm any findings.

If you notice your child has an unexplained lump or mass, be sure to have it evaluated by an experienced team like the one at CHOP, and make sure your child’s physician performs an imaging study before any type of surgery.

Unless the lump is considered 100% benign (non-cancerous) based on the imaging studies, a biopsy should be performed of the lesion before any surgery is considered. Determining whether the lump is cancerous or not will impact which treatment is best for your child.

Treatment for soft tissue sarcomas

Treatment for soft tissue sarcomas vary, depending on the type of tumor, tumor genetics, size, location, and rate of growth.

The Bone and Soft Tissue Tumor Program at CHOP takes a team approach to treatment. Your child’s care team may include experts from several areas of medicine, including pediatric orthopaedic surgery, diagnostic or interventional radiology, oncology, radiation oncology and more, who collaborate to provide your child with individualized care and the best possible outcomes.


Chemotherapy refers to medicines that help fight cancer. They are given to your child orally (by mouth) or injected into a vein. Comprehensive genetic testing will be utilized to help define the optimal treatment for your child’s tumor. Chemotherapy is used routinely in some types of soft tissue sarcomas such as rhabdomyosarcoma and synovial sarcoma.

In some types of soft tissue sarcomas, such as infantile fibrosarcoma, we now regularly use targeted therapies that can be given by mouth to block the genetic changes that cause the tumor without many of the side effects traditionally associated with chemotherapy, such as hair loss and weakened immune system.

Other types of soft tissue sarcomas may not require chemotherapy.

Local Control

There are two options that may be used alone or together to treat the primary tumor: surgery and radiation therapy. We use a multidisciplinary approach to determine which option is best for each patient based on the location of their tumor.


Surgical removal of soft tissue tumors may be used alone or in conjunction with chemotherapy or radiation therapy.

The goals of surgery are twofold:

  • To remove the tumor
  • To restore function at the site of the tumor

More than 90% of children with soft tissue sarcomas can be treated with limb-sparing (also known as limb-salvage) and reconstructive surgery. CHOP surgeons regularly perform these complex surgeries and are constantly working to improve outcomes for children with the most difficult-to-treat tumors.

Limb-sparing surgery is performed under general anesthesia. It involves cutting out the tumor and a margin of healthy tissue surrounding it. Depending on the size and location of the tumor, as well as your child’s age and stage of growth, orthopaedic and plastic surgeons may use a variety of reconstructive methods to restore your child’s body function. Reconstructive surgery, if necessary, will occur on the same day the tumor is removed.

Reconstruction may include:

  • Skin graft, in which a doctor removes skin from the child’s own thigh or buttocks to use it to cover and protect the area where the tumor was removed
  • Rotational muscle or fasciocutaneous flap, in which a doctor uses a child’s own muscle or skin near the surgery site, and rotates it to fill the area where the tumor was removed to provide a soft-tissue reconstruction
  • Free muscle or fasciocutaneous flap, in which a doctor uses muscle or skin from the child’s own body, relocates it, and then reconnects the blood vessels to the tissue that was moved in the area where the tumor was removed
  • A free bone flap, in which a piece of bone from a donor site is moved, based on its blood supply, to reconstruct the bony defect

In extremely rare cases — because of the size or location of the tumor — a soft tissue sarcoma cannot be removed with limb-sparing surgery. In these rare situations, it may be necessary to perform an amputation of the affected limb.

After surgery for a soft tissue sarcoma, your child should expect to stay two to five days in the hospital.

Surgical safety

Though surgery for soft tissue tumors is highly effective, we understand that any surgery can be a stressful experience for your child and family. At CHOP, we offer a wealth of resources about how to prepare your child for surgery and what to expect during surgery

Additionally, we employ numerous best practices before, during and after surgery to decrease the risk of infection and increase positive outcomes. For more details about safety protocols at Children's Hospital of Philadelphia, see safety in surgery

Radiation therapy

Depending on your child’s individual situation, radiation therapy may be recommended. The radiation destroys or damages cancer cells so they cannot grow or spread.

The goal of radiation treatment is to damage as many cancer cells as possible, while limiting harm to nearby healthy cells. To protect healthy cells, your doctor will carefully plan the dose of radiation and space the treatment over time.

We offer pediatric proton therapy in collaboration with Penn Medicine at the Roberts Proton Therapy Center. Proton therapy is an innovative form of radiation treatment that is only available at very few hospitals across the nation. The greatest benefit of proton therapy is that it delivers most of its energy to a very narrow field at the location of the tumor — making it less damaging to the surrounding healthy tissue.

Follow-up care

During follow-up visits, diagnostic testing of the tumor site or other areas may be recommended to closely monitor your child’s health and make sure there is no recurrence.

After surgery, your child may require some pain medication until the surgical site heals and ongoing physical therapy. Most children are encouraged to resume their regular daily activities, like school, social events and play time, as soon as possible.

Your child will return to see the orthopaedic surgeon one to two weeks after surgery, then again every three months for two years post-surgery. Regular monitoring by trained clinicians is strongly encouraged for the next 10 years to monitor for possible recurrence of the growth and manage any side effects of treatment.

Follow-up care and ongoing support and services are available at our Philadelphia Campus and throughout our CHOP Care Network. Our team is committed to partnering with parents and referring physicians to provide the most current, comprehensive and specialized care possible for your child.

If continued monitoring into adulthood is needed, your child can continue to see some of the same doctors. CHOP’s Bone and Soft Tissue Tumor Program works closely with Penn Medicine. For families who live farther away and need continued monitoring, our clinical professionals will help your child transition to adult care near your home.


As with any cancer, survival depends on the type of cancer, the age of your child, how much the tumor has grown and how well your child tolerated treatment.

Some children treated for soft tissue sarcomas develop complications years later. Our Cancer Survivorship Program provides information about the potential long-term effects of the specific treatment your child received, including ways of monitoring and treating these effects.

Reviewed by Kristy L. Weber, MD, FACS, Alexandre Arkader, MD, Stephen J. Kovach, III, MD, Theodore W. Laetsch, MD

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