Patients were either concurrently positive for JAK2 V617F and BCR::ABL1 at initial diagnosis (5/10, 50%; patients #1 to #5, cohort A) or BCR::ABL1 emerged in a preexisting JAK2 V617Fpos MPN (5/10, 50%, patients #6 to #10, cohort B). This evidence concerns the gene BCR and myeloproliferative disorder.