Cancers and Tumors

Bone Tumors and Sarcoma

What Are Bone Tumors and Sarcoma?

Tumors are lumps of tissue that form when cells divide uncontrollably.

When tumors start inside the skeleton, such as in the leg bones, the arm bones or the ribs, they are called bone tumors. When they start inside other tissues, such as muscles, fat or blood vessels, they are called soft tissue tumors.

Tumors can be either benign or malignant.

Benign tumors are not cancerous and do not spread from their original (primary) site. They can, however, come back (recur) at their original site.

Malignant tumors are cancerous and have the potential to spread cancer cells to other parts of the body (metastasis).

Both bone tumors and soft tissue tumors can be either benign or malignant. When these tumors are cancerous, they are called sarcomas.

Types of Sarcoma

Ewing sarcoma

Ewing sarcoma can start in any bone in the body. This includes the leg bones, the ribs, the pelvis and the arm bones. Other tumors in the Ewing sarcoma family can develop in soft tissue.


Osteosarcoma starts in cells that are supposed to build new bone. Instead, these cells destroy bone and weaken it. This can happen in any bone.

In children, it most often starts near the knee, either in the thighbone (femur) or the shin bone (tibia). Sometimes it spreads to other bones or the lungs. Very rarely, it begins outside the bone.

Soft tissue sarcomas

Soft tissue sarcomas can start in any of the soft tissues that connect or support other structures. These include muscles, tendons, fat, blood vessels, lymph vessels, nerves and the soft tissues in and around joints.

Most often soft tissue sarcomas affect the muscles that attach to bones and allow us to bend our joints (skeletal muscles). This type is called rhabdomyosarcoma. It can start in any muscle in the body, including around the head, next to the brain, in the bladder or in an arm or leg.

Rarely, children get other kinds of soft tissue sarcomas.

Bone Tumors and Sarcoma in Children

Any child may get a bone tumor (benign or malignant) or sarcoma. Doctors do not know what causes the disease. Some factors may increase a child's risk for sarcoma, but most children who have sarcoma have none of these risk factors.

For example, children with certain uncommon inherited conditions have a greater risk of developing soft tissue sarcoma. Most children with sarcoma don't have this risk factor. They developed the disease for unknown reasons.

Age may affect risk. Adolescents and young adults develop osteosarcoma more often than any other age group. The Ewing family of tumors is most common in adolescents. Soft tissue sarcoma is rare in children at any age.

Bone Tumors and Sarcoma Stages

Staging refers to the way doctors classify cancer. They may consider where it is in the body, whether it has spread, its size and several other factors.

The staging system is different for each type of cancer and sarcoma. Some cancer is staged only after surgery. The cancer's stage, along with your child's health and other factors, helps doctors choose treatments.

Osteosarcoma and Ewing tumors of the bone may be localized (in only one part of the body) or metastatic (spread to another part of the body).

Soft tissue sarcomas, including rhabdomyosarcoma, may be divided into four stages based on these factors:

  • Whether the tumor is more than two inches across
  • Whether the tumor has spread to lymph nodes  
  • Whether the tumor has spread to other areas of the body
  • How much the tumor resembles normal tissue and how fast it is growing

Bone Tumors and Sarcoma at Seattle Children's

At Children's, our doctors and other members of your child's team have worked with many children with a bone tumor or sarcoma. It's important to work with doctors who have experience treating these types of cancer.

We have a Bone Tumor and Sarcoma Clinic for children where orthopedic surgeons and cancer doctors called oncologists see patients. In the clinic a team can focus on the care of sarcomas.

We offer the most current treatment options and surgeries. Our surgeons are leaders in operations called "limb sparing," which means removing areas of cancer in bone without having to amputate any part of an arm or leg.

Dr. Douglas S. Hawkins is a member of the Children's Oncology Group (COG) Bone Sarcoma Disease Committee and chair of the COG Soft Tissue Disease Committee. He is the study chair for two international clinical trials, one for Ewing sarcoma and the other for rhabdomyosarcoma.

COG is an international organization of childhood cancer specialists who conduct studies on many forms of childhood cancer. With these committees, Dr. Hawkins is responsible for directing studies for childhood soft tissue sarcomas across North America.

Dr. Hawkins is the principal investigator for all COG studies at Children's.

Bone Tumor and Sarcoma Survival Rates

Doctors who treat people with cancer use five-year survival rates as a way to measure treatment success. The five-year survival rate means the percentage of patients with the disease who are alive five years after their disease was diagnosed.

For both Ewing sarcoma and osteosarcoma, our rates are up to 8 points higher than the national average. Read more childhood cancer statistics.

Read more about the Bone Tumor and Sarcoma Clinic, cancer-related programs and services, and research at Children's Hospital.