Myeloproliferative neoplasms, namely the BCR::ABL1-negative subtypes such as polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF), are identified as clonal hematopoietic stem cell conditions marked by the aberrant proliferation of myeloid lineages. This evidence concerns the gene BCR and essential thrombocythemia.