TET2 and myeloproliferative neoplasm: Three distinct TET2 mutations were present as heterozygous founder clonal mutations in the primary cells of 2 patients, Pts 3 and 7 (Figure 5F), indicating that TET2 mutations may represent early events but that additional genetic mutations are required to transform a chronic MPN to BP, such as KRAS mutation in Pt 3 (Figure 4B) and JAK2V617F, MPL, and TP53 mutations in Pt 7 (Figure 3B).