ETV6 deletion is a common additional abnormality in patients with myelodysplastic syndromes or acute myeloid leukemia and monosomy 7

proportions ranging from 0% to 38% have also been reported, depending on the criteria for the excessive Lyonization definition, the type of XCIP, and even the tissue type.However, given that CIN patients and healthy controls are age-matched, the differences in clonality assessment obtained should be taken into account as they cannot be attributed to the influence of age-related skewing.Furthermore, no significant difference was found in age distribution between subjects (patients or controls) with clonal and those with non-clonal XCIP, suggesting that our results are unlikely to be biased by age.The pathophysiological significance of the clonal populations identified in CIN patients is obscure.They might indicate a contraction of the stem cell pool resulting in support of hematopoiesis by one or a few stem cells, as previously described in aplastic anemia and hypoplastic myelodysplastic syndromes (MDS).4 Alternatively, they might imply an early event in a transformation process and although malignant evolution has been rarely reported in CIN, a thorough long-term follow up of patients with clonal populations is needed.12 The clonal XCIP in our patients should not be interpreted as indicative for MDS diagnosis because the majority of these patients had a long history of stable disease.Overall, we have provided evidence for possible clonal hematopoiesis in CIN.However, clonality data cannot be currently used as a diagnostic criterion for the disease and further studies with newer technologies, such as comparative genomic hybridization and single nucleotide polymorphism arraybased karyotyping, are required to confirm clonal patterns of hematopoiesis in these patients.