Atypical t(15;17)(q13;q12) in a patient with all-trans retinoic acid refractory secondary acute promyelocytic leukemia: a case report and review of the literature.

A 69-year-old woman developed microgranular acute promyelocytic leukemia (APL-M3) 10 months after receiving adjuvant cyclophosphamide, doxorubicin, and paclitaxel for breast cancer. Replicate bone marrow aspirate karyotypes contained a translocation between the long arms of chromosomes 15 and 17, but not at breakpoints typical for APL. Fluorescence in situ hybridization paints and RARalpha/PML cosmid probes verified that the breakpoints on chromosomes 15 and 17 were proximal to both the PML and RARalpha genes; t(15;17)(q13;12). Although the patient received induction chemotherapy and a several month trial of all-trans retinoic acid (ATRA), there was no clinical improvement or hematological remission. We suspect that this patient developed postchemotherapy secondary APL with an atypical t(15;17), which rendered her leukemic cells unresponsive to ATRA therapy.