A t(17;20)(q21;q12) masking a variant t(15;17)(q22;q21) in a patient with acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is genetically characterized by a reciprocal translocation between chromosomes 15 and 17, the t(15;17)(q22;q21), which results in the fusion gene PML/RARA. A small proportion of patients with APL have complex or simple variants of this translocation. We report the case of a 31-year-old woman with APL (FAB-M3 classical form) carrying an apparently balanced translocation t(17;20)(q21;q12) masking a t(15;17)(q22;q21) confirmed by fluorescence in situ hybridization (FISH) and molecular studies. The patient was treated with an all-trans-retinoic acid (ATRA) plus anthracycline-based protocol and achieved complete remission, with no recurrence to date. These results illustrate the usefulness of combining cytogenetics, FISH, and reverse transcription–polymerase chain reaction (RT-PCR) methods to evidence the PML/RARA fusion gene in cases with morphologic suspicion of APL with variant or cryptic t(15;17).