The MLL-AF9-expressing HSC-derived leukemic cells exhibited a high nucleus/cytoplasm ratio with a B-ALL phenotype, i.e., CD19+CD10+CD20-sIgMlow/-sIgDlow/-CD44hiMHC-I+MHC-IIhi and negative for other lineage markers, i.e., CD33-CD15low/-CD14-CD11b-CD3-CD4-CD8-CD56-. The gene discussed is KMT2A; the disease is acute lymphoblastic leukemia.