Abstract
Intrachromosomal amplification (iAMP) of chromosome 21 entity is associated with a dismal outcome in B cell Acute Lymphoblastic Leukemia (B-ALL). This cytogenetic abnormality is caused by a novel mechanism; breakage-fusion-bridge cycles followed by chromothripsis along with major gross rearrangements in chromosome 21. Charts of B-ALL diagnosed at King Faisal Specialist Hospital and Research Center between 2005 and 2015 were reviewed. iAMP is a rare entity occurring at around 2.4% of all pediatrics BALL. No statistically significant difference was found among patients with iAMP21, patients with extra copies of 21 and other patients with B-ALL. The reported adverse prognostic effect of iAMP21 could be due to other coexistent adverse factors, including older age at the time of diagnosis. The most common associated abnormality in our population in addition to the hyperdiploidy was ETV6/RUNX1.