Major differences between WHO and FAB Replacing the morphologic terms of LI and L2 ALL with an immunologic classification consisting of precursor-B and precursor- t lymphoblastic leukemias that are further subgrouped by cytogenetic abnormalities Grouping L3 ALL with Burkitts lymphoma Lowering the blast count from 30 to 20% for the diagnosis of AML, with elimination of the myelodysplastic subgroup of refractory anemia with excess blasts in transformation RAEB-IT) Revision of the mds subdivision based on number of dysplastic lineages, presence of ringed sideroblasts, and blast percentage Recognition of distinct cytogenetic AML subtypes New category of AMl with multilineage dysplasia with or without an antecedent mds New category of Therapy-Related AML New category of Acute Leukemia of Ambiguous lineage Inclusion of a pure erythroid leukemia(M6b)in the AML Not Otherwise Categorized subgroup Recognition of the rare acute basophilic leukemia also in the AML Not Otherwise Categorized subgroupMajor differences between WHO and FAB