Multilineage dysplasia in NPM1-mutated AML. (A) Dysgranulopoiesis (Dys G) in a case of NPM1-mutated AML showing myeloid cells with hypogranulated cytoplasm and pseudo-Pelger cells. Bone marrow, Pappenheim staining. (B) Dyserythropoiesis (Dys E) in a case of NPM1-mutated AML showing nuclear irregularity with fragmentation, a mitosis, and multinucleation of red precursors. Bone marrow, Pappenheim staining. (C) Dysmegakaryopoiesis (Dys M) in a case of NPM1-mutated AML showing 2 dysplastic megakaryocytes with multiple nuclei. Bone marrow, Pappenheim staining. (A-C) All images were collected using a Zeiss Axio Imager.A1, 63×/1.4 oil objective Plan-Apochromat; 10×/23 eyepiece Sony camera 3CCD HD, Model MC-HD 1/3 Horn imaging DHS solution. (D) Lightcycler-based melting curve analyses showing different NPM1 mutation types in AML with MLD changes: A (nt959insTCTG), D (nt959insCCTG), I (nt959insCTTG), X (nt959insTTCC), and wild-type patients. (E-F) Expression of CD34 by multiparameter flow cytometry. A case with NPM1 mutation and MLD changes demonstrating a lack of expression of CD34 (E, note the different levels of CD33 expression between myeloblasts and monoblasts). A different AML MLD⁺ case without NPM1 mutation showing a strong expression of CD34 with a part of the population lacking CD33 expression (F). Slightly modified from Falini et al⁸⁸  with permission.