Chromosomal rearrangements, particularly intra- and inter-chromosomal translocations, may fuse two genes to create an oncogene (e.g.BCR–ABL fusion gene in chronic myeloid leukaemia) or, in a small number of cases, inactivate a tumour suppressor gene (e.g.TEL–AML fusion repressing the tumour suppressor TEL1). The gene discussed is ETV6; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.