BCR and essential thrombocythemia: BCR::ABL1-negative myeloproliferative neoplasms (MPN) encompass a group of chronic hematologic cancers, including essential thrombocythemia (ET), polycythemia vera (PV), and primary myelofibrosis (PMF), characterized by clonal proliferation of hematopoietic stem cells and a high burden of symptoms that worsen over time (Palandri et al. 2018, 2025; Mesa et al. 2016; Harrison et al. 2017a; Manz et al. 2024).