Like in adults, in pediatric CML the vast majority of breakpoints cluster in a small region of the major (M-bcr) breakpoint while alternate, less common breakpoints cluster in the minor bcr (m-bcr) and very rarely further upstream in the BCR gene, in the so-called micro bcr (μ-bcr) [22,23,24]. The gene discussed is BCR; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.