A major reason for these poor outcomes is the loss of a key tumor suppressor gene, TP53, which resides at this locus and whose loss allows leukemic cells to survive when exposed to chemotherapy.3, 4 Recent clinical studies in CLL have shown that in addition to TP53 deletion, mutations in the p53 pathway also result in poor outcomes.5 Even though p53 mutations have been implicated in exacerbating leukemic phenotypes in CLL, mutations in this gene are not commonly examined in clinical settings. The gene discussed is TP53; the disease is B-cell chronic lymphocytic leukemia.