GPT and acute promyelocytic leukemia: The use of HR by ALT positive cells can result in several cellular abnormalities which are considered “hallmarks” of activation of the pathway, including: 1) ALT-associated promyelocytic leukemia bodies (APBs), which are present in 5-35% of ALT cells [4], 2) telomere length heterogeneity ranging from 2 kb to greater than 20 kb in length [4,5], and 3) the appearance of circular ECTR [6,7], the latter of which is considered to be most reliable of all of the markers [2].