Approximately 7 percent of childhood malignancies are soft tissue sarcomas. One half of these malignancies are rhabdomyosarcomas (RMS) originating in striated muscle. Although adult sarcomas primarily involve the extremities, RMS in children can occur in any anatomic location, including locations with no skeletal muscle. The most common sites are in the genitourinary systems, extremities, head, and neck. A review by Andrassy emphasizes the importance of tumor location and individualized management in the prognosis of RMS in children.
The clinical presentation depends on tumor location and size. About one third of cases originate in the head and neck, and 25 to 35 percent of these have central nervous system involvement. The presentation may be of an unexplained mass or cranial nerve palsies, meningeal symptoms, or even respiratory problems caused by brainstem infiltration. About 26 percent of pediatric RMS cases occur in the genitourinary system. The painless swelling may initially be diagnosed as a hernia, hydrocele, or varicocele in boys and may cause bleeding, vaginal discharge, or a mass in girls. In adolescents, RMS more commonly presents as a painless mass in the extremities, but up to one half of cases have spread to lymph nodes by the time of diagnostic biopsy. Regardless of site, biopsy is key to diagnosis and staging. Excisional biopsy is possible in some cases, depending on the location and size of the lesion. Even with clear margins, regional node sampling is recommended following wide excisional biopsy to plan radiation therapy or other subsequent treatment and more accurately provide prognosis. Depending on the situation, computed tomography or magnetic resonance imaging assessment of the primary site, regional nodes, or areas of likely metastasis also may be indicated for diagnosis and staging. The Intergroup RMS Study system of staging correlates with overall survival (see accompanying table). Five-year survival for patients in group I is more than 90 percent following complete excision, whereas rates for patients in group IV average 30 to 35 percent.
Complete local excision is the recommended initial treatment of RMS, except for lesions of the orbit, vagina, or bladder. In these locations, chemotherapy, with or without radiation, plus limited surgery, provides results comparable with more aggressive surgery. Regardless of site or type of tumor, surgery must be carefully planned to balance the need for tumor removal against loss of function and mutilation. Overall, surgical treatment has become less aggressive, with more patients being managed by limited initial surgery followed by chemotherapy or subsequent surgeries. The traditional mainstay of chemotherapy for RMS has been combinations of vincristine, dactinomycin, and cyclophosphamide. Other drugs such as doxorubicin, ifosphamide, actinomycin, topotecan, and irinotecan may be used as part of combination therapy targeting specific tumor types. Radiation (usually external beam) is used selectively to enhance local tumor control.
|Group I||Localized disease, completely removed|
|Confined to muscle or organ of origin|
|Infiltration outside organ or muscle of origin; regional nodes not involved|
|Group II||Total gross resection with evidence of regional spread|
|Grossly resected tumor with microscopic residual|
|Regional disease with involved nodes, completely resected with no microscopic residual|
|Regional disease with involved nodes grossly resected, but with evidence or microscopic residual and/or histologic involvement of the most distal regional node in the dissection|
|Group III||Incomplete resection, or biopsy with presence of gross disease|
|Group IV||Distant metastasis|
The management of RMS depends on the site and type of tumor. Surgery is often limited in the head and neck for cosmetic reasons and because metastasis to cervical nodes is rare. Biopsy plus chemotherapy and radiation can result in 90 percent survival rates in orbital lesions without the need for extensive surgery. In RMS of the bladder, more conservative surgical treatments have resulted in 85 percent survival, with 60 percent of patients retaining bladder function. The treatment of paratesticular RMS is controversial because of the high probability of retroperitoneal lymph node involvement, especially in adolescents. Radical inguinal orchiectomy is recommended, but experts disagree on the extent of retroperitoneal node dissection. Adjuvant chemotherapy combined with surgery results in survivals of more than 90 percent. For lesions of the female genital tract, management is now based on local resection followed by chemotherapy with or without selective radiotherapy. Radical surgical excision is no longer recommended. The worst outlook in RMS is in patients with lesions in the extremities. Surgery must balance limb sparing and good functional outcome with eradication of disease. Up to one half of patients with RMS of the extremities have positive lymph nodes and require radiation therapy.