In WHO 2016 guidelines regarding diagnosis and treatment of chronic myeloid, first of all, the leukemia criteria of acceleration phase identification were revised. Despite these changes, the guidelines are still not standardized and differ significantly as compared to other guidelines of most important European and world scientific societies. These changes resulted, however, in necessity to diagnose acceleration phase much more frequently than to date, according to WHO. It is particularly significant for patients already treated with first line tyrosine‑kinase inhibitors, as it increases the percentage of patients with indications for allogenic hematopoietic stem cell transplantation. The case of the patient with the decision about second line treatment made before 2016 shows that in the tyrosine‑kinase inhibitors era the changes in WHO guidelines contrast with everyday practice and tendency to marginalize the role of transplanting hematopoietic cells in this disease classification unit. It seems necessary to conduct a discussion, and perhaps to plan and perform an appropriate clinical trial, to provide more data and allow to optimize the treatment in such controversial cases.