Mutational analysis for a single or concurrent clonal driver in patients with CEL has been reported in a variety of genes involved in myeloproliferation, such as JAK2, additional sex combs like 1 (ASXL1), chaperonin containing TCP1 subunit 6B (CCT6B), tet methylcytosine dioxygenase 2 (TET2), enhancer of zeste homolog 2 (EZH2), Casitas B-lineage lymphoma (CBL), or signal transducer and activator of transcription (STAT). The gene discussed is CCT6B; the disease is Chronic Eosinophilic Leukemia, Not Otherwise Specified.