Moreover, in 1/2 cases with PMF histology obvious after TKI, the presence of fibrosis at initial CML diagnosis could have been a possible clue for PMF, although fibrosis alone is not sufficient for PMF diagnosis as fibrosis may be found even in CML; in this case, BCR::ABL1 and JAK2 were both present from initial CML diagnosis, however PMF features became obvious after CMR of CML (4). This evidence concerns the gene JAK2 and chronic myelogenous leukemia, BCR-ABL1 positive.