OncoLink en espanõl
Share
Types of Cancer > Pediatric Cancers > Sarcomas: Rhabdomyosarcoma > Overview
Rhabdomyosarcoma
Neha Vapiwala, MD
Affiliation:
Abramson Cancer Center of the University of Pennsylvania
Last Modified: April 27, 2004
What is a sarcoma?
Sarcoma is a general medical term that refers to any cancer of the bone, muscle, or other connective tissue, such as cartilage and tendons. Sarcoma has sometimes been defined as a "tumor of fleshy consistence", made up of cells similar to those of the growing fetus, but without proper development.
Sarcomas can occur in both children and adults, both males and females. In fact, there are many different types of sarcomas, depending on where the cancer cells grow and how they appear under a microscope. These different types are in turn associated with different clinical behavior, which naturally influences how they are treated.
What is a rhabdomyosarcoma?
Rhabdomyosarcoma is the most common type of soft tissue sarcoma found in children. It is still a rare cancer overall, accounting for about 3.5% of all childhood cancers. About 250 new cases of rhabdomyosarcoma are diagnosed in the United States every year.
Rhabdomyosarcomas specifically start growing in the skeletal muscle of soft tissues (the muscles that are used in voluntary actions, also called striated muscle). Rhabdomyosarcomas can occur anywhere in the body, but usually occur in the head, neck, bladder, vagina, extremities and the trunk.
The name itself comes from a combination of 3 smaller words: rhabdo means "rod-shaped", myo is muscle, and sarcoma is the type of cancer, as described above. Rhabdomysarcoma cells tend to look rod-shaped under a microscope, and they have several features of muscle cells. Normally, as a fetus develops in the womb, cells called rhabdomyoblasts "grow up" to become the skeletal muscles of the body. When these cells do not mature correctly, but continue to multiply abnormally, a rhabdomyosarcoma results.
Who gets rhabdomyosarcomas, and why?
Over 85% of all rhabdomyosarcomas occur in infants, children, and teenagers . T here is no specific geographic location or racial background that has been associated with higher rates of rhabdomyosarcoma. However, Asian and black children have a lower annual incidence than do white children. There also appears to be a male predominance, as boys are about 1.5 times more likely than girls to get rhabdomyosarcoma.
It is known that rhabdomyosarcomas are associated with specific chromosomal abnormalities. What exactly causes these mutations, however, is not known. One possibility is that these mutations are inherited, (ie: genetic, passed on from one or both parents, "nature" as opposed to "nurture"). It has been observed that a large number of kids with rhabdomyosarcomas also have congenital anomalies of various organ systems (abnormal development of heart, gut, brain, etc). Also, an increased frequency of rhabdomyosarcoma is diagnosed in children with certain rare genetic disorders, such as neurofibromatosis type 1. As of now, however, no clear genetic link has been found.
The other possibility is that the responsible mutations are caused by something in the environment, rather than the genes (nurture). Unlike many adult cancers, there are no definitive environmental conditions that increase the chance of getting rhabdomyosarcoma. No connection has ever been found between rhabdomyosarcoma and exposure to toxic substances, environmental pollution, radiation (eg: x-rays during pregnancy), or physical injury (trauma). Not even tobacco smoke has been linked with development of this or any other childhood cancers, although cigarette smoke is clearly and certainly harmful to children in many other ways. There is some data to suggest an association with parental use of marijuana and cocaine, but no truly definitive environmental cause has emerged.