Although peripheral blood primary CLL cells showed lower Ki67 levels than MEC1 cells (range of Ki67+ cells: 2%-20%) (Figure 5C, 5D), in EZH2high cases most Ki67+ cells co-expressed EZH2 (Figure 5C, 5E): in more detail, in the four EZH2high cases analysed, 75-97% of Ki67+ cells were also EZH2+. This evidence concerns the gene MKI67 and B-cell chronic lymphocytic leukemia.