Table 1A. Bone marrow minimal histological criteria for refractory cytopenia of childhood.^4,5 Refractory cytopenia of childhood is defined as persistent cytopenia with <5% blasts in bone marrow and <2% blasts in peripheral blood. The criteria of dysplasia must be fulfilled in ≥2 cell lineages or ≥10% of cells within one cell lineage on bone marrow aspirate smears.

Cellularity	Erythropoiesis	Granulopoiesis	Megakaryopoiesis
Variable	A few clusters of ≥20 erythroid precursors. Arrest in maturation, with increased number of proerythroblasts. Increased number of mitoses.	No minimal diagnostic criteria	Unequivocal micromegakaryocytes; immunohistochemistry is obligatory (CD61, CD41, CD42b); other dysplastic changes in variable numbers