Chronic Myeloid Leukemia (CML) belongs to a group of myeloid neoplasms called myeloproliferative neoplasms. Besides CML, the 2016 World Health Organization (WHO) guidelines for chronic myeloproliferative neoplasms include six other categories: Chronic Neutrophilic Leukemia (CNL), Polycythemia Vera (PV), Primary Myelofibrosis (PMF), Essential Thrombocythemia (ET), Chronic Eosinophilic Leukemia not otherwise specified, and Myeloproliferative neoplasms (MPN) unclassifiable (MPN-U). CML is the most common of the myeloproliferative diseases. It is a clonal neoplasm of pluripotent stem cells that involves all of the myeloid lineage as well as some lymphoid cells.
The principal manifestation of CML is leukocytosis with granulocytic proliferation of mature and immature cells that involve the bone marrow, peripheral blood, spleen, and liver.
The natural course of CML starts with the chronic phase (CML-CP) that shows leukocytosis, granulocytic proliferation, followed by disease progression to an accelerated phase (CML-AP) and the blastic phase (CML-BP). The blastic phase of CML resembles acute leukemia. Patients may die during the accelerated or blastic phase from bone marrow failure which is manifested by infection, bleeding, or anemia.