Namely, there is a lack of comprehensive knowledge about molecular biology of paediatric BCR::ABL1-neg MPNs, including myelofibrosis, and therefore, there is a lack of prognostic factors and prognostic-scores, and in consequence there is a lack of clear indications to assure appropriate selection of paediatric patients for allo-HCT. Here, BCR is linked to myelofibrosis.