FLT3 and acute promyelocytic leukemia: (5) In APML. The risk of thrombosis has been correlated with raised white blood cell count, presence of bcr3 isoform subtype of PML/RARα and fms-like tyrosine kinase 3 internal tandem duplication (FLT3 ITD) mutations, and expression of CD2 and CD15 [17].