The BCR::ABL1 rearrangement, encoded by the Philadelphia (Ph1) chromosome and resulting from t(9;22)(q34;q11) translocation, is the molecular hallmark of chronic myeloid leukemia (CML), a well-known myeloproliferative neoplasm [1]. The gene discussed is BCR; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.