Rhabdomyosarcoma (RMS):Highly malignant tumor in which the tissue of origin is pluripotent mesenchyme.
- M/C soft-tissue sarcoma of the head and neck in childhood
- 4% of all pediatric malignancies
- 10% of all cases occur in the orbit
- Embryonal variant (M/C, 80% cases)
- Alveolar variant (worst prognosis): Small round, densely appearing cells loosely arranged with septae similar to lung alveoli
- Botryoid variant: Subepithelial grape-like aggregates of tumour cells
- Pleomorphic variant
- Proptosis developing rapidly over weeks (80–100% cases)
- Globe displacement (80% cases) which is usually downward and outward because two-thirds of these tumors are supero-nasal
Imaging:USG, CT-scan, MRI
IRS post-surgical staging system:
- Group I: localized disease, completely resected (excisional biopsy).
- Group II: microscopic disease remaining after biopsy.
- Group III: gross residual disease remaining after biopsy.
- Group IV: distant metastasis present at onset.
European pediatric Soft tissue sarcoma Study Group (EpSSG) protocol (EpSSG-RMS-2005):
- Group I: chemotherapy consisting of VA.
- Groups II and III: chemotherapy VA ± Ifosfamide ± rediotherapy
- Group IV: Intensified chemotherapy regimen (IVA and doxorubicin) followed by one year of maintenance chemotherapy and radiotherapy