Multilineage dysplasia in NPM1-mutated AML. (A) Aberrant cytoplasmic expression of NPM1 in leukemic cells of the 3 hematopoietic cell lineages. (BM biopsy, APAAP staining; original magnification ×400). (B) An area showing several dysplastic megakaryocytes detected by immunostaining against LAT (linker for activation of T cells) (BM biopsy, APAAP staining; original magnification ×400). (C) An area occupied by numerous leukemic cells of erythroid cell lineage that show surface expression of glycophorin (Gly; BM biopsy, APAAP staining; original magnification × 400). (D) Leukemic cells stained for glycophorin (brown) and cytoplasmic NPM1 (blue) (BM biopsy, immunoperoxidase [brown]/APAAP [blue]; original magnification ×400). (E) Diagnostic algorithm for the differential diagnosis between NPM1-mutated AML and AML-MRC. *No prior cytotoxic or radiation therapy; no recurrent cytogenetic abnormalities defining distinct AML entities of 2017 WHO classification.