In the present report, starting from the presentation of two cases with a long history of JAK2-positive PMF subsequently developing CML with BCR::ABL1 translocation acquisition, we performed a systematic review with the purpose to improve our understanding of this particular setting of MPNs with co-occurring BCR::ABL1 translocation and JAK2 mutation, focusing on clinical and laboratory signs and on bone marrow (BM) morphological features, which may represent clues of coexistence of Ph-negative MPNs and CML. The gene discussed is JAK2; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.