Which cytogenetic abnormality is diagnostic of acute promyelocytic leukemia (APL)?

Which cytogenetic abnormality is diagnostic of acute promyelocytic leukemia (APL)?

• A. t(9;22)
• B. t(15;17)
• C. t(8;14)
• D. inv(16)

Answer: (B)

The defining cytogenetic finding for acute promyelocytic leukemia is the translocation between chromosomes 15 and 17 that creates the PML-RARA fusion gene. This fusion disrupts retinoic acid receptor signaling and blocks differentiation of myeloid precursors, causing an accumulation of abnormal promyelocytes. Its presence is highly specific for APL and directly guides therapy with all-trans retinoic acid (ATRA) and arsenic trioxide. Other listed abnormalities point to different diseases: the 9;22 translocation is BCR-ABL seen in CML (and some ALL); the 8;14 translocation involves MYC and is classic for Burkitt lymphoma; inv(16) relates to CBFB-MYH11 in AML M4Eo, not APL.

The defining cytogenetic finding for acute promyelocytic leukemia is the translocation between chromosomes 15 and 17 that creates the PML-RARA fusion gene. This fusion disrupts retinoic acid receptor signaling and blocks differentiation of myeloid precursors, causing an accumulation of abnormal promyelocytes. Its presence is highly specific for APL and directly guides therapy with all-trans retinoic acid (ATRA) and arsenic trioxide. Other listed abnormalities point to different diseases: the 9;22 translocation is BCR-ABL seen in CML (and some ALL); the 8;14 translocation involves MYC and is classic for Burkitt lymphoma; inv(16) relates to CBFB-MYH11 in AML M4Eo, not APL.