Overview

Soft tissue sarcoma is cancer that develops in the tissues that support and connect the body. It can occur in fat, muscle, nerves, tendons, joints, blood vessels, or lymph vessels. Cancer begins when normal cells begin to change and grow uncontrollably, forming a mass called a tumor. A tumor can be benign (noncancerous) or malignant (cancerous, meaning it can spread to other parts of the body). In general, sarcoma is uncommon, accounting for about 1% of all cancers.

Rhabdomyosarcoma is a type of soft tissue sarcoma that begins in mesenchymal cells (immature cells that normally become muscle). It develops in a type of muscle called striated muscle. Striated muscles are the skeletal voluntary muscles, which are those muscles that people can control.

Rhabdomyosarcoma can occur anywhere in the body:

• Head and neck, about 39% of all rhabdomyosarcoma cases (parameningeal sites [near the membranes covering the brain], 24%; eye orbit, 8%; other head and neck locations, 7%)
  
  
• Urinary or reproductive organs, about 29% of cases
  
  
• Arms or legs, about 15% of cases
  
  
• Other sites (trunk [torso], intrathoracic, biliary tract, retroperitoneal, pelvic and perineal sites), about 17% of cases

Types of rhabdomyosarcoma

Each rhabdomyosarcoma tumor is classified as either favorable or unfavorable based on its histology, which is what the cells look like under a microscope. The terms “favorable” and “unfavorable” refer to the appearance of the cancer cells. In general, the more cancer cells look like normal cells, the more “favorable” they are.

Favorable histology tumors include the following:

Embryonal rhabdomyosarcoma. This is the most common type of rhabdomyosarcoma, frequently found in the head and neck and in the reproductive and urinary organs.

Botryoid rhabdomyosarcoma. This is one subtype of embryonal rhabdomyosarcoma, found most often in hollow organs, such as the bladder and vagina.

Spindle rhabdomyosarcoma. This is another subtype of embryonal rhabdomyosarcoma, found most often in the area around the testicles.

Unfavorable histology tumors include the following:

Alveolar rhabdomyosarcoma. This is a more aggressive type of rhabdomyosarcoma, found most often in the arms, legs, or trunk of the body.

Pleomorphic and undifferentiated rhabdomyosarcoma. These are the rarest types of rhabdomyosarcoma, found most commonly in the arms, legs, or trunk.

This section covers rhabdomyosarcoma diagnosed in children. Learn more about soft tissue sarcoma in adults.

Statistics

About 350 people are diagnosed with rhabdomyosarcoma each year, with 90% occurring in people under age 25. About 60% of childhood rhabdomyosarcomas are diagnosed in those under age 10. Rhabdomyosarcoma accounts for about 4% of all new childhood cancer cases each year in the United States. It is the most common soft tissue sarcoma in children. The five-year relative survival rate (the percentage of people who survive at least five years after the cancer is detected, excluding those who die from other diseases) of people with rhabdomyosarcoma depends on the tumor location, stage, and the child’s age.

Cancer survival statistics should be interpreted with caution. These estimates are based on data from thousands of cases of this type of cancer, but the actual risk for a particular individual may differ. It is not possible to tell a person how long he or she will live with rhabdomyosarcoma. Because the survival statistics are measured in five-year intervals, they may not represent advances made in the treatment or diagnosis of this cancer.

Statistics source: the American Cancer Society.

Find out more about basic cancer terms used in this section.