BACKGROUND: Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm caused by the t(9;22)(q34;q11.2) translocation, known as the Philadelphia chromosome (Ph+), which generates the BCR::ABL1 fusion oncogene central to CML pathogenesis. The gene discussed is BCR; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.