Basophilia Predicts Poorer Outcomes in Essential Thrombocythemia, Polycythemia Vera, Primary Myelofibrosis, and Myeloproliferative Neoplasm, Unclassifiable

Basophils are hematopoietic cells derived from myeloid progenitor cells and are found in increased numbers in some myeloid neoplasms, particularly chronic myeloid leukemia (CML). Marked basophilia is a poor prognostic indicator in CML and defines accelerated phase according to the revised 4th edition World Health Organization (WHO4R) classification and the International Consensus Classification (ICC).

Basophilia is less well-documented in the classic BCR::ABL1-negative myeloproliferative neoplasms (MPNs) essential thrombocythemia (ET), polycythemia vera (PV), and primary myelofibrosis (PMF). The clinical behavior of these BCR::ABL1-negative MPNs is heterogeneous, with varying propensity to progress to fibrotic or blast phase. Prior studies have reported that patients with primary or secondary myelofibrosis (MF) with high basophil counts have increased risk of progression to blast phase, shortened survival, and more frequent CALR mutations [1].

The significance of basophilia across ET, PV, and PMF, as well as its association with driver mutations other than the classic JAK2 V617F, CALR, and MPL, have not been previously characterized. In the current study, we examined a broad cohort of MPNs to determine associations of basophilia with clinical and molecular features and patient outcome.