TP53 is a well known tumor suppressor gene that is mutated in wide variety of cancers. Loss of function mutations (missense, nonsense and frameshift mutations) of TP53 have been described in 10-20% of CLL cases and TP53 gene defects tend to be enriched among cases with unmutated IGH variable regions; in some series, TP53 mutations have been reported in approximately 15%-18% of IGHV unmutated CLL cases . TP53 mutations appears to be less common in other types of CLL (eg, less than 5% of IGHV3-21-expressing CLL carried a TP53 defect according to one study). Mutations of TP53 in CLL have been found together with del17p and mutations in other genes such as NOTCH1 and SF3B1. Mutations and deletions of TP53 appear to represent adverse prognostic markers in chronic lymphocytic leukemia.