In 3/43 cases, BCR::ABL1 and JAK2 were both positive at CML occurrence and presented a similar growth either remaining both positive and at the same allele burden before and after TKI (1/3 cases) (39), or both increasing during the disease course, without TKI (1/3 cases) (45) or both decreasing under TKI (1/3 cases). Here, JAK2 is linked to chronic myelogenous leukemia, BCR-ABL1 positive.