‐PB monocyte count > 1000/ul, splenomegaly, absence of BCR‐ABL1‐One of the below:‐Somatic mutation in PTPN11, KRAS, or NRAS‐NF1 diagnosis or NF1 mutation‐Germ line CBL mutation and LOH of CBL‐Chromosomal abnormality such as monosomy 7‐Two of the following: HbF increased for age, myeloid or erythroid precursors on PB smear, GM‐CSF hypersensitivity on colony assay, hyperphosphorylation of STAT5. The gene discussed is CBL; the disease is Splenomegaly.