Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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July 19, 2010
Rhabdomyosarcoma of Orbit
- Rhabdomyosarcoma is the most common childhood soft tissue sarcoma.
- Origin: primitive mesenchymal cells committed to skeletal muscle differentiation (rhabdomyoblasts).
- Pathology: p53 tumor suppressor gene mutation, loss of heterozygosity (LOH) at 11p15 locus. PAX-FKHR gene fusion.
- Subtypes: Embryonal (50%), Alveolar involves extremities and trunk, Pleomorphic (rare) involves extremities.
- Age: 70% under 12 years, 43% under 5 years of age. More common in Caucasians.
- Associated anomalies: NF1, Li-Fraumeni and Beckwith-Wiedemann syndrome. Rarely with hereditary retinoblastoma or XRT-induced.
- Prognosis: Location: Orbit best (80-90% disease-free survival). Parameningeal worst (40-50%). Type: Alveolar worse than embryonal and pleomorphic.
- CT: Soft tissue mass with variable contrast enhancement +/- bone destruction. Role to evaluate osseous erosion.
- MRI: Relative to muscle: isointense on T1WI, hyperintense T2WI. Role to evaluate intracranial and perineural spread. Include neck for mets.
- DDx: Metastatic Neuroblastoma, Lymphangioma, and Hemangioma.
- Treatment: Surgical debulking, chemotherapy, RT.
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