A 40-year-old man has acute myeloid leukaemia with WBC 60,000/uL. Bone marrow shows monocytic blasts with abundant abnormal eosinophils whose granules stain purple-blue rather than orange-red. Cytogenetics reveal inv(16)(p13q22). This lesion fuses which genes, and what prognostic category does it confer?

• A PML-RARA, intermediate prognosis
• B RUNX1-RUNX1T1, poor prognosis
• C CBFB-MYH11, favourable prognosis ✓
• D FLT3-ITD, favourable prognosis

Explanation

inv(16) disrupts the CBFB gene at 16q22 and joins it to MYH11 at 16p13. The fusion disrupts the core binding factor transcription complex, defining the M4eo subtype with characteristic abnormal eosinophil granules. It belongs to the favourable-risk group alongside t(8;21), with better complete remission and cure rates using cytarabine-based therapy. FLT3-ITD confers adverse risk, and PML-RARA belongs to acute promyelocytic leukaemia, not this morphology.

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.