BCR::ABL1 transcript can be classified into major (M-BCR), minor (m-BCR), and micro (μ-BCR) depending on the breakpoint in BCR. M-BCR is the predominant transcript type in CML and the only one that has been standardised at International Scale (IS). The gene discussed is ABL1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.