To verify the clinical relevance of CD123 as a target for immunotherapy in BPDCN, we first analyzed the bone marrow (BM) of 8 patients with newly diagnosed BPDCN to determine CD123 expression in comparison to BM blasts of 28 patients with newly diagnosed acute myeloid leukemia (AML) and 13 AML patients in remission. This evidence concerns the gene IL3RA and acute myeloid leukemia.