This suggests that CD99 plays a role in leukemogenesis [11] In AML cells, CD99 levels increase with the Fms-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) mutation, which is found in approximately 30% of patients and is linked to disease progression as well as a higher risk of relapse [83,84]. The gene discussed is FLT3; the disease is acute myeloid leukemia.