A 4-year-old boy develops rapidly progressive proptosis of the right eye over three weeks, with the globe displaced downward and laterally. A firm mass is palpable in the superonasal quadrant of the orbit. Biopsy shows small round blue cells positive for desmin and myogenin.

• A Embryonal rhabdomyosarcoma ✓
• B Granulocytic sarcoma
• C Neuroblastoma metastasis
• D Ewing sarcoma

Explanation

Rhabdomyosarcoma is the commonest primary malignant orbital tumour of childhood, presenting as rapidly progressive proptosis with a superonasal mass. Positivity for desmin and myogenin confirms skeletal muscle differentiation. Neuroblastoma metastasis also affects young children but is usually bilateral with adrenal or abdominal primary disease, and granulocytic sarcoma stains for myeloperoxidase rather than muscle markers.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.