This is, for example, the case of chronic eosinophilic leukemia associated with the 4q12 deletion (resulting in the loss of the CHIC2 gene) responsible for the fusion of the FIP1L1 and PDGFRA genes (F/P + chronic eosinophilic leukemia (or myeloid neoplasm with F/P-associated HES according to the most recent WHO and International Consensus Classification nomenclatures) [4–6]. This evidence concerns the gene FIP1L1 and Chronic Eosinophilic Leukemia, Not Otherwise Specified.