ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: Deletions of 5' ABL1 and/or 3' BCR sequences at the der(9) chromosome in patients with classical and variant Ph translocations [27] have been shown to have adverse prognostic value in CML patients treated with interferon [28], although their impact in patients being treated with tyrosine kinase inhibitors is controversial [29-31].