Prospective study of 174 de novo acute myelogenous leukemias according to the WHO classification: subtypes, cytogenetic features and FLT3 mutations.

We report a prospective study of 174 unselected adult de novo acute myeloid leukemia (AML) cases diagnosed using the WHO classification. Of those, 57 (33%) were AML with recurrent cytogenetic abnormalities, 41 were (24%) AML with multilineage dysplasia, 74 (42%) were AML not otherwise categorized, and two were acute leukemias of ambiguous lineage. Clonal cytogenetic abnormalities were detected in 64% of the WHO AML cases with t(15;17) (15%), t(8;21) (12%), +8 (11%), -7/del7q (8%) and del9q (5%) being the most common ones. The FLT3/ITD mutations (FMS-like tyrosine kinase 3/internal tandem duplication) were observed in 12% of the WHO AML cases, which is much lower than ones in the literature, while the 6% incidence of the FLT3-activating loop mutations (either FLT3/D835 or FLT3/I836) was comparable with others. Both mutations were associated with leukocytosis. Our study also suggests that the FLT3 mutations are biomarkers independent of cytogenetic characteristics.