Oligoclonal hematopoiesis at the time of clonal evolution to –7 MDS in SAA patients. (A) Dominant hematopoietic clone VAF in 13 SAA patients at the time of clonal evolution to MDS with −7. Each patient’s mutations with VAF >0.25 are shown. (B-C) VAF of acquired mutations in UPN#1 and UPN#2, with neutrophil count. Direct Sanger sequencing confirmed the presence of mutations and VAF. The upper part of the graph shows representative hematoxylin-eosin staining of the core biopsy and CD34 antigen staining at the time of clonal evolution. The images were taken on an Olympus BX41 microscope with an Olympus DP72 camera, using a 4× UPlanFL N Olympus objective (original magnification ×20). Neutrophil count (left y-axis) is shown by blue bars. VAF of acquired mutations (right y-axis) at various time points from diagnosis of SAA until diagnosis of MDS are shown in red and green line graphs. Arrows on the x-axis mark ISTs and time to progression to MDS.