BCR and acquired polycythemia vera: Polycythemia vera (PV) is a BCR::ABL1-negative myeloproliferative neoplasm (MPN) characterized by constitutive JAK-STAT signaling due to acquired mutations in the JAK2 gene, which is present in the majority of patients (>90%), leading to elevated red cell mass, increased blood viscosity, chronic inflammatory state, and high cardiovascular risk [1].