FLT3 mutations in a 10 year consecutive series of 177 childhood acute leukemias and their impact on global gene expression patterns

During 1995-2004, 209 children/adolescents were diagnosed with acute lymphoblastic or myeloid leukemia (ALL, AML) in Southern Sweden, of which 177 (85%), comprising 128 B-lineage ALL, 34 AML, and 15 T-cell ALL, could be analyzed for internal tandem duplications (ITD) and activating point mutations in the second tyrosine kinase domain (ATKD) of FLT3. Seventeen (10%) FLT3 mutations (6 ITD, 11 ATKD; mutually exclusive) were detected. None of the T-cell ALL harbored any mutations. ITD and ATKD were found in 2% and 6% of the B-lineage ALL and in 12% and 9% of the AML, being particularly common in high hyperdiploid ALL (14%), ALL (20%), and AML (23%) with 11q23/MLL rearrangements, and in AML with a normal karyotype (60%). All ATKD-positive AML with MLL rearrangements harbored the t(9;11)(p21;q23). Global gene expression data were available for 76 of the B-lineage ALL and 19 of the AML, of which 6 (8%) and 3 (16%) had FLT3 mutations, respectively. No distinct expression pattern associated with FLT3 mutations was identified.