According to the fifth edition of the World Health Organization (WHO) criteria, MPNs include chronic myeloid leukemia (CML), which is defined by the presence of the Philadelphia chromosome and BCR::ABL1 fusion gene, polycythemia vera (PV), essential thrombocythemia (ET), primary myelofibrosis (PMF), chronic neutrophilic leukemia (CNL), chronic eosinophilic leukemia (CEL), juvenile myelomonocytic leukemia, and myeloproliferative neoplasms, not otherwise specified. This evidence concerns the gene BCR and acquired polycythemia vera.