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%