Next-generation sequencing of a poorly differentiated carcinoma of unknown primary reveals an in-frame fusion of ETV6-NTRK3. This fusion gene is most characteristically associated with which tumor type that guides diagnosis?
- A Alveolar rhabdomyosarcoma
- B Ewing sarcoma
- C Congenital fibrosarcoma / secretory carcinoma of breast ✓
- D Synovial sarcoma
Correct answer: C. Congenital fibrosarcoma / secretory carcinoma of breast
Explanation
ETV6-NTRK3 is the hallmark fusion of both congenital (infantile) fibrosarcoma and secretory carcinoma of the breast (and salivary gland); it results from t(12;15)(p13;q25). Alveolar rhabdomyosarcoma carries PAX3/7-FOXO1; Ewing sarcoma carries EWSR1-FLI1; synovial sarcoma carries SS18-SSX. Identifying this fusion is clinically important because it predicts response to TRK inhibitors (larotrectinib/entrectinib).
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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