This premalignant stage may be characterized by one or more somatic mutations in genes associated with hematological neoplasms, such as predominantly TET2, DNMT3A, ASXL1, but also JAK2, SF3B1, SRSF2, TP53 or PPM1D [104,110,111,112,113] and is present in 10–20% of healthy, older individuals over age 70, but only in 1% of healthy individuals below age 50 [104,111]. The gene discussed is JAK2; the disease is hematopoietic and lymphoid system neoplasm.