Rhabdomyosarcoma is a childhood 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. Rhabdomyosarcoma belongs to a group of tumors known as soft-tissue sarcomas and is the most common cancer in this group.
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.
Although rhabdomyosarcoma can occur almost anywhere in the body, the cancer has a predilection for several sites:
Head and neck region (about 35%), usually in the orbit or nasopharyngeal passages: Most common among school-aged children
GU system (about 25%), usually in the bladder, prostate, or vagina: Usually occurring in infants and toddlers
Extremities (about 20%): Most common among adolescents
Trunk/miscellaneous sites (20%)
About 15 to 25% of children present with metastatic disease. The lung is the most common site of metastasis; bone, bone marrow, and lymph nodes are other possible sites.
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. Regional lymph node spread occurs frequently, and metastases in the lungs, bone marrow, and lymph nodes can occur and usually do not cause symptoms.
Masses are evaluated by CT, although head and neck lesions are often better defined by MRI. Diagnosis of rhabdomyosarcoma is confirmed by biopsy or excision of the mass.
The standard metastatic evaluation includes chest CT, a bone scan, and bilateral bone marrow aspiration and biopsy.
Prognosis is based on
Cancer location (eg, prognosis is better with nonparameningeal head/neck and nonbladder/nonprostate GU cancers)
Completeness of resection
Presence of metastasis
Age (prognosis is worse for children < 1 yr of age or > 10 yr
Histology (embryonal histology is associated with a better outcome than alveolar histology)
Combinations of these prognostic factors place children in a low-risk, intermediate-risk, or high-risk category. A complex risk stratification system exists based on two staging systems (see the National Cancer Institute's stage information for rhabdomyosarcoma). 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 of rhabdomyosarcoma 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 responsive 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 vincristine, actinomycin D, cyclophosphamide, doxorubicin, ifosfamide, and etoposide. Topotecan and irinotecan are newer drugs that have activity against this cancer.
Radiation therapy is generally reserved for children with residual bulk disease or microscopic residual tumor after surgery and for children with intermediate-risk or high-risk disease.