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Updated: Jun 22 2021


  • summary
    • Rhabdomyosarcomas are malignant tumors of the primitive mesenchyme that come in 4 sub-types: embryonal, alveolar, botryoid, and pleomorphic.
    • The embryonal and botryoid sub-types most commonly present in young children, the alveolar sub-type most commonly occurs in young adults, and the pleomorphic sub-type most commonly occurs in older patients.
    • Diagnosis is made with a biopsy. Immunostains are positive for desmin, myosin and vimentin.
    • Treatment is usually wide surgical excision with chemotherapy or radiation depending on the sub-type.  
  • Epidemiology
    • Incidence
      • Rhabdomyosarcoma is the most common sarcoma in children
  • Etiology
    • Four sub-types of rhabdomyosarcoma
      • Embryonal
        • occurs in infants and young children
      • Alveolar
        • occurs in adolescents and young adults
      • Botryoid
        • occurs in infants and young children, typically in the vagina
        • aka Sarcoma botryoides or "bunch of grapes"
      • Pleomorphic
        • tends to occur in older patients 40-70yrs
    • Genetics
      • alveolar rhabdomyosarcoma has a common t(2;13) translocation
        • forms Pax3-FKHR fusion protein
        • associated with a high risk metastatic disease
    • Metastasis
      • nodal metastasis are known to occur with rhabdomyosarcoma
        • consider sentinel lymph node biopsy as part of treatment
      • bone marrow biopsy is required for staging
        • bone marrow metastases have been shown to portend a worse prognosis
  • Symptoms
    • Presentation
      • rapidly growing painless mass
      • most lesions occur in the head/neck, genitourinary system, or retroperitoneum
  • Imaging
    • CT
      • CT of the chest is required for staging of disease
    • MRI
      • non-diagnostic but crucial for treatment planning
      • rhabdomyosarcoma images appear like many other soft tissue sarcomas
        • dark on T1, bright on T2
  • Histology
    • Characteristic histology includes
      • Embryonal
        • small round blue cell tumor
        • skeletal muscle-like cross-striations can occur
        • based on the stage of neoplastic cell development
      • Alveolar
        • poorly differentiated round cells with multinucleated giant cells
        • cellular aggregates are surrounded by dense fibrous septae
      • Pleomorphic
        • multiple cell types present
        • difficult to differentiate from other pleomorphic sarcomas
    • Immunohistochemistry
      • MyoD1 positive
      • myoglobin positive
      • myosin positive
      • desmin positive
      • vimentin positive
  • Differential
      • Differential of Rhabdomyosarcoma
      • Malignant small round blue cell
      • Rhabdomyosarcoma
      • o
      • Neuroblastoma
      • o
      • Lymphoma
      • o
      • Leukemia
      • o
      • Ewing's sarcoma
      • o
      • Metastatic disease
      • o
  • Treatment
    • Nonoperative
      • chemotherapy alone
        • indications
          • only indicated in select patients with widespread metastatic disease.
      • radiation therapy alone
        • indications
          • can be used for unresectable tumors or close/positive margins
    • Operative
      • wide surgical excision with chemotherapy
        • indications
          • pediatric rhabdomyosarcoma
          • chemotherapy is not effective for adult rhabdomyosarcoma
        • technique
          • common agents include vincristine, dactinomycin, cyclophosphamide
      • wide surgical excision with radiation therapy
        • indications
          • adult pleomorphic rhabdomyosarcoma
  • Prognosis
    • 5-year survival
      • Embryonal - 80%
      • Alveolar - 60%
      • Botryoid - uniformly fatal, less than 30% of patients live 5 years from the time of diagnosis
      • Pleomorphic - 25%
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