In this case report, FISH analysis detected RUNX1-RUNX1T1 gene rearrangement in the absence of cytogenetic abnormality of t(8;21), which suggests the presence of unvailed t(8;21).     ///    [Near-tetraploidy acute myeloid leukemia with RUNX1-RUNX1T1 rearrangement due to cryptic t(8;21)]..     ///    This is the first case report of tetraploidy or near-tetraploidy AML with cryptic RUNX1/RUNX1T1 in Korea. 