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L. Zalmai et al.
8,674]). In two cases, blasts expressed CD4, whereas CD56 was never expressed. The blastic population did not express markers strongly associated with the pDC (cTCL1, CD303 and CD304) or cDC (CD1c, CD11c) line- ages.
Associated pDC were constantly CD123+high, CD4+/+low and CD303+ (100%), with CD304 expression in most cases (13 of 15, 87%) and none of them expressed CD56. The immaturity marker CD34 was expressed in 33% of cases, whereas TdT in only one case out of nine tested.
The CD123 expression level was significantly higher on pDC than on the immature CD34+ blasts (MFIR: 172.9 [range, 12.5-482.6] vs. 15.58 [range, 2.5-63.1] on CD34+ blasts, P<0.0001; MFI: 20,836 [range, 10,755-45,746] vs. 2,309 [range, 465-8,674] on CD34+ blasts, P<0.0001) (Figure 3A and B). cTCL1 was expressed in pDC (nine of 12 cases, 75%) at a statistically lower level (MFIR: 5.3 [range, 0.6-22.6]; MFI: 2,473 [range, 487-20,684]) than in the 21 BPDCN cases (MFIR: 34 [range, 6.0-96.0], P<0.0001; MFI: 13,990 [range, 2,186-125,568], P=0.0006)
Figure 4. Mutation profile of plasmacytoid dendritic cell-acute myeloid leukemia. Mutations detected by next-generation sequencing with variant allele frequencies (VAF), or Sanger sequencing (especially for ASXL1). Abnormalities in plasmacytoid dendritic cells-acute myeloid leukemia (pDC-AML) and blastic pDC neoplasms (BPDCN) are depicted in: bright blue (monoallelic mutation); dark blue (biallelic mutation); white (absence of mutation); grey (not available). ¤Percentage of cells cor- responds to flow cytometry, quantification on the sample used for phenotyping, possibly diluted by peripheral blood (all cases exhibited more than 20% of blasts on bone marrow smears). $Analyses performed on sample obtained after induction of chemotherapy, 70 days after diagnosis. £Fluorescence in situ hybridization (FISH) 7q36 on case N16: loss of EZH2 in 91 of 200 nuclei. ***VAF not available because ASXL1 c.1934dupG;p.Gly646TrpfsX12 was confirmed by Sanger sequencing. Mono: monocytes.
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