CALR-mutated myeloproliferative neoplasms: Refining molecular risk beyond the driver.

Calreticulin (CALR)-mutated myeloproliferative neoplasms (MPNs) are generally associated with favourable outcomes, yet considerable heterogeneity persists across the disease course. Mawalkar et al. provide long-term data across essential thrombocythaemia (ET), post-ET myelofibrosis (MF) and primary MF, highlighting the prognostic relevance of additional somatic mutations. The contribution of co-mutational context, variant allele frequency (VAF), disease origin and timing of molecular assessment remains incompletely defined. Commentary on: Mawalkar et al. Outcome heterogeneity in CALR-mutated myeloproliferative neoplasms. Br J Haematol 2026 (Online ahead of print). doi: 10.1111/bjh.70859.