Morphology and immunophenotype of NPMc⁺ AML with AK. The figure shows the morphologic and immunohistologic features of a representative example of NPM1-mutated AML with AK 47,XX,+8,der(19)t(13;19)(q12;q13) (top panel). These features are identical to those observed in the typical NPM1-mutated AML cases with NK. (Middle left) Diffuse marrow infiltration by leukemic cells with myelomonocytic appearance. The arrow points to a dysplastic megakaryocyte (paraffin section from bone marrow biopsy; hematoxylin-eosin; ×1000). (Middle right) Leukemic cells are CD34⁻. The single arrow indicates a dysplastic megakaryocyte, while the double arrows indicate a CD34⁺ vessel. (Bottom left) Myelomonocytic leukemic cells and a dysplastic megakaryocyte (arrow) show aberrant cytoplasmic expression of nucleophosmin (NPM1), indicating they belong to the same clone; cells showing nucleus-restricted expression of nucleophosmin represent normal residual hemopoietic precursors. (Bottom right) Leukemic cells and a dysplastic megakaryocyte (arrow) show nucleus-restricted positivity for C23/nucleolin. (Middle right and bottom panels) Immunostaining of paraffin sections from bone marrow biopsy using the alkaline phosphatase monoclonal anti-alkaline phosphatase (APAAP) technique; hematoxylin counterstaining; ×1000. All images were collected using an Olympus B61 microscope and a UPlan FL 100×/1.3 NA oil objective; Camedia 4040, Dp_soft Version 3.2; and Adobe Photoshop 7.0.