Even if we acknowledge that the blast proportion should be enumerated in BM aspirate and cannot generally be extrapolated by immunohistochemical examinations, except for cases of dry tap [10,69,95], we have considered that immunohistochemical reaction for NPM1 protein, carried out on BM trephine biopsy, when NPM1 mutation is detected by PCR analysis in patients with MDS or MDS/MPN, may interestingly allow to precisely evaluate multilineage BM cells with NPMc+ staining, belonging to the NPM1-mutated leukemic clone regardless of blast morphology [69,102]. This evidence concerns the gene NPM1 and myelodysplastic syndrome.