An Original Complex Rearrangement Involving Chromosomes 9, 11, and 14, Harboring a Complex KMT2A Gene Rearrangement in an Infant With Mixed-phenotype Acute Leukemia.

KMT2A gene rearrangements represent the most frequent group of abnormalities in childhood leukemia (~70% of cases), with over 120 rearrangements described. The investigation of KMT2A rearrangements is still a vast field to be explored. Several studies have been characterizing different outcomes and leukemogenic mechanisms, depending on the translocation partner gene involved in childhood KMT2A-r leukemias. Therefore, the detection of the translocation partner gene, including in the context of complex rearrangements, may help to better delineate the disease. Here, we describe clinical and molecular cytogenetic data of a new complex variant translocation, involving chromosomes 9, 11, and 14, presenting a KMT2A gene extra copy and rearrangements, in an infant with de novo mixed-phenotype acute leukemia.