Rhabdomyosarcoma is a cancer arising from embryonal mesenchymal cells that have potential to differentiate into skeletal muscle cells. It can arise from almost any type of muscle tissue in any location, resulting in highly variable clinical manifestations. Cancers are typically detected by CT or MRI, and diagnosis is confirmed by biopsy. Treatment involves surgery, radiation therapy, and chemotherapy.

Rhabdomyosarcoma is the 3rd most common extra-CNS solid cancer in children (after Wilms' tumor and neuroblastoma). Nonetheless, it accounts for only 3 to 4% of all childhood cancers. Incidence of rhabdomyosarcoma in children is 4.3/million/yr. Two thirds of cancers are diagnosed in children < 7 yr. The disease is more common among whites than blacks (largely because frequency is lower in black girls) and is slightly more common among boys than girls.

Histology: There are 2 major histologic subtypes:

• Embryonal: Characterized by loss of heterozygosity on chromosome 11p15.5
• Alveolar: Associated with a translocation involving PAX3 or PAX7, regulators of transcription during neuromuscular development (chromosome 2;13 or 1;13 translocation)

Location: Although rhabdomyosarcoma can occur almost anywhere in the body, the cancer has predilection for several sites:

• Head and neck region, usually in the orbit or nasopharyngeal passages: 35 to 40%, most common among school-aged children
• GU system, usually in the bladder, prostate, or vagina: 25%, usually occurring in infants and toddlers
• Extremities: 20%, most common among adolescents

Fewer than 25% of children present with metastatic disease.

Symptoms and Signs

Children do not typically have systemic symptoms such as fever, night sweats, or weight loss. Usually, children present with a firm, palpable mass or with organ dysfunction due to impingement on the organ by the cancer.

Orbital and nasopharyngeal cancers may cause tearing, eye pain, or proptosis. Nasopharyngeal cavity cancers may cause nasal congestion, a change in voice, or mucopurulent discharge.

GU cancers cause abdominal pain, a palpable abdominal mass, difficulty urinating, and hematuria.

Extremity cancers appear as firm, indiscrete masses anywhere on the arms or legs. Metastases occur frequently, especially in the lungs, bone marrow, and lymph nodes, and usually do not cause symptoms.

Diagnosis

• CT or MRI
• Biopsy or excision

Masses are evaluated by CT, although head and neck lesions are often better defined by MRI. Diagnosis is confirmed by biopsy or excision of the mass. The standard metastatic evaluation includes chest CT, a bone scan, and bone marrow aspiration and biopsy.

Prognosis

Prognosis is based on

• Cancer location (eg, prognosis is better with head and GU cancers)
• Extent of resection
• Presence of metastasis
• Age (more favorable in younger children)
• Histology (embryonal histology is associated with a better outcome than alveolar histology)

Combinations of these prognostic factors place children at low, intermediate, or high risk. Treatment intensifies with each risk category, and overall survival ranges from > 90% in children with low-risk disease to < 50% in children with high-risk disease.

Treatment

• Surgery and chemotherapy
• Sometimes radiation therapy

Treatment consists of surgery, chemotherapy, and sometimes radiation therapy. Complete excision of the primary cancer is recommended when it can be done safely. Because the cancer is so sensitive to chemotherapy and radiation therapy, aggressive resection is discouraged if it may result in organ damage or dysfunction.

Children in all risk categories are treated with chemotherapy; the most commonly used drugs are vincristineSome Trade Names
ONCOVIN
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, actinomycin D, cyclophosphamideSome Trade Names
CYTOXAN
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, doxorubicinSome Trade Names
ADRIAMYCIN
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, ifosfamideSome Trade Names
IFEX
MITOXANA
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, and etoposideSome Trade Names
ETOPOPHOS
VEPESID
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. TopotecanSome Trade Names
HYCAMTIN
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and irinotecanSome Trade Names
CAMPTOSAR
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are newer drugs that have activity against this cancer; they are being investigated in some frontline treatment regimens.

Radiation therapy is generally reserved for children with residual cancer after surgery and for children with intermediate-risk or high-risk disease.

Last full review/revision January 2009 by David N. Korones, MD

Content last modified February 2012