A 12-year-old presents with a mid-shaft femoral lesion showing 'onion-skin' periosteal reaction on plain radiograph. Biopsy reveals small round blue cells arranged in sheets. The chromosomal translocation characteristic of this diagnosis is:
- A t(12;16)(q13;p11) involving FUS-DDIT3 fusion
- B t(X;18)(p11;q11) involving SS18-SSX fusion
- C t(11;22)(q24;q12) involving EWS-FLI1 fusion ✓
- D t(2;13)(q35;q14) involving PAX3-FOXO1 fusion
Correct answer: C. t(11;22)(q24;q12) involving EWS-FLI1 fusion
Explanation
Ewing sarcoma classically presents with diaphyseal lesions in long bones in children, with the characteristic onion-skin periosteal reaction and small round blue cell histology. The pathognomonic translocation is t(11;22)(q24;q12), producing the EWS-FLI1 fusion transcript (in ~85% of cases). t(12;16) is seen in myxoid liposarcoma, t(X;18) in synovial sarcoma, and t(2;13) in alveolar rhabdomyosarcoma. Treatment includes neoadjuvant chemotherapy (vincristine-doxorubicin-cyclophosphamide alternating with ifosfamide-etoposide) plus local control with surgery or radiation.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.