Cryptic Rearrangement of theKMT2AGene in a B-cell Acute Lymphoblastic Leukemia

This case highlights the need to supplement banding cytogenetics with appropriate molecular (cyto)genetic techniques whenever the karyotype does not reveal characteristic aberrations. Although KMT2A rearrangements in both lymphoblastic and myeloid acute leukemias usually arise through karyotypically visible chromosomal recombinations, this is not always the case.