Comprehensive High-Sensitivity Mutation Profiling in MPNs: Diagnostic and Prognostic Implications.

Background/Objectives: Myeloproliferative neoplasms (MPNs) are clonal hematopoietic stem cell disorders driven by somatic mutations, most commonly those in JAK2, CALR, and MPL. While conventional molecular testing often focuses on these canonical mutations, emerging data suggest that additional mutations and low-variant-allele-frequency (VAF) subclones may contribute to disease progression and prognosis. Methods: We applied ultra-deep targeted sequencing with an error-correction algorithm to analyze bone marrow and peripheral blood samples from 134 patients with essential thrombocythemia (ET), polycythemia vera (PV), primary myelofibrosis (PMF), secondary myelofibrosis (MF), or post-MPN acute leukemia. Targeted sequencing panels were used to detect disease-associated and clonal driver mutations. Matched germline controls were not systematically available. Results: Low-VAF variants (<5%) were identified in 4/16 (25%) CALR, 3/7 (43%) MPL, and 9/11 (82%) TP53 mutations. In contrast, all TP53 mutations identified at leukemic transformation had VAFs > 5%, suggesting clonal expansion during progression. Paired sequencing at initial MPN diagnosis and leukemic transformation was available for three patients. JAK2 p.V617F VAFs differed according to treatment timing (Kruskal-Wallis test, p = 0.0138), with lower VAFs observed in untreated patients; however, this association may be influenced by treatment-selection confounding. Mutations in ASXL1 and SRSF2 were occasionally observed in ET and secondary MF, although their prognostic significance remains uncertain. Progression analyses were exploratory because of the limited number of events and longitudinally sampled patients, and formal survival or prognostic modeling was not performed. Conclusions: Ultra-deep error-corrected sequencing enables sensitive detection of low-VAF mutations in MPNs, including subclonal events potentially missed by less sensitive assays. These findings demonstrate the potential utility of high-sensitivity panel-based sequencing for molecular characterization of MPN, while larger longitudinal studies are required to establish the prognostic and clinical significance of these findings.