Acute promyelocytic leukemia with unusual morphological features, absence of the t(15,17) and rearranged PML/RAR alpha genes.

cute promyelocytic leukemia (APL) is a subtype of acute myeloid leukemia with unique morphologic, cytogenetic, molecular and clinical features. Besides the classical hypergranular variant, there is also a cytological microgranular variant with significant clinical implications in both children and adults. Moreover, a basophilic form and a hyperbasophilic microgranular variant have been described, suggesting further morphological heterogeneity. t(15;17) is considered the specific cytogenetic marker for both the hypergranular and microgranular variants, and diagnosis of APL could be questionable in the absence of this cytogenetic abnormality. PML and RARa genes are involved by t(15;17) and their rearrangement is considered the molecular counterpart of the translocation. However, the existence of cases lacking this translocation but showing rearrangements of the PML/RARa genes has recently been reported. The availability of a more sensitive approach to APL diagnosis would obviously be of great importance in view of the thera-