Health A-Z

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Harvard Medical School

Rhabdomyosarcoma

What Is It?

Rhabdomyosarcoma is a rare cancer seen in children more than adults. In about two-thirds of cases, rhabdomyosarcoma occurs in a child younger than 10. It is a soft tissue tumor that typically appears in one of three locations: the head and neck region (35% to 40% of cases), the urinary tract and reproductive organs (25% of cases), or the arms and legs (10% of cases). It also can occur on the trunk. Doctors classify this cancer based on the way the cells appear under a microscope; most are either embryonal (60% of cases) or alveolar (20% of cases).

• Embryonal. Tumors tend to develop at the back of the throat, in the ear canal or in the urinary or reproductive tracts. In general, this is a limited, localized cancer that responds well to treatment and rarely spreads (metastasizes).

• Alveolar. Tumors tend to be aggressive and hard to treat. They often begin in the arms and legs, especially in older children and teenagers.

• There are two other varieties known as anaplastic rhabdomyosarcoma and undifferentiated sarcoma that are quite rare.

Rhabdomyosarcoma is often associated with specific genetic abnormalities. Certain people may be prone to developing this type of cancer, as part of an increased susceptibility to developing multiple cancers.

In the United States, rhabdomyosarcoma strikes approximately 5 in every 1 million children each year. Children are more likely to develop rhabdomyosarcoma if they already have Li-Fraumeni syndrome or neurofibromatosis (type I), or if they have an older relative who has been diagnosed with early-onset breast cancer or adrenal cancer. Rhabdomyosarcoma is more common in children whose parents have used recreational drugs, especially marijuana or cocaine, and whose fathers smoke, but this association needs further study. Likewise, children of mothers who were exposed to multiple courses of antibiotics during pregnancy have also been associated with a high incidence of rhabdomyosarcomas.