t(15;17) hypergranular acute promyelocytic leukemia (M3) developing into a t(3;6) M3 without t(15;17) at relapse.

This report describes a case of acute promyelocytic leukemia (APL) M3. At diagnosis, the specific t(15;17) translocation was observed. After chemotherapy including retinoic acid, a complete remission was achieved and the karyotype became normal. At relapse of the M3 leukemia, the t(15;17) clone was no longer observed but a t(3;6) translocation was then detected. Several hypotheses for this unusual cytogenetic course of APL are discussed.