A 14-year-old with Ewing sarcoma of the proximal humerus is being staged. Which chromosome translocation is characteristically associated with Ewing sarcoma?
- A t(X;18)(p11;q11) — SYT-SSX fusion
- B t(12;16)(q13;p11) — FUS-DDIT3 fusion
- C t(11;22)(q24;q12) — EWS-FLI1 fusion ✓
- D t(2;13)(q35;q14) — PAX3-FOXO1 fusion
Correct answer: C. t(11;22)(q24;q12) — EWS-FLI1 fusion
Explanation
Ewing sarcoma is characterized by translocation t(11;22)(q24;q12) in ~85% of cases, resulting in the EWS-FLI1 fusion gene; a variant t(21;22) gives EWS-ERG. These are detected by FISH or RT-PCR and are diagnostic. t(X;18) is characteristic of synovial sarcoma (SYT-SSX). t(12;16) is myxoid liposarcoma (FUS-DDIT3). t(2;13) is alveolar rhabdomyosarcoma (PAX3-FOXO1). Recognizing these translocations is essential for round cell tumor differential diagnosis on NEET PG.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.