Fifty percent of T cell prolymphocytic leukemias display deletions at 22q11, the location of SNF5. Additionally, conditional deletion of SNF5 in mice leads to T cell lymphomas with short latency and 100% penetrance.50 Generally, specific mutations or translocations affecting SWI/SNF subunits may produce gain-of-function properties that result in an oncogenic SWI/SNF complex. Here, SMARCA1 is linked to T-cell prolymphocytic leukemia.