CLINICOPATHOLOGICAL FEATURES AND P53 EXPRESSION IN LEFT-SIDED SPORADIC COLORECTAL CANCERS WITH AND WITHOUT MICROSATELLITE INSTABILITY

Defects in mismatch repair (MMR) can result in the development of a 'm utator phenotypc', manifest as an increase in DNA replication errors ( RERs). Patients with hereditary non-polyposis colorectal cancer (HNPCC ) have germline mutations in MMR genes, These patients develop carcino mas of the colon and other specific sites at a significantly earlier a ge than patients with sporadic carcinomas, RERs are found in the cance rs from patients with HNPCC and have been demonstrated in 10-20 per ce nt of sporadic colorectal cancers (CRCs), Loss of MMR may simply accel erate tumour development, but it is also possible that these tumours f ollow a different carcinogenetic pathway from tumours with intact MMR. In particular, it has been suggested that p53 mutations occur less of ten in RER-positive (RER+) sporadic colorectal cancers, in this study, the clinico-pathological features and frequency of p53 overexpression in 17 left-sided RER+ CRCs were compared with 35 left-sided RER - CRC s, No differences mere found in the age and tumour stage at presentati on, mucinous differentiation, or Jass prognostic grouping between thes e two types of CRC, Thirteen out of 17 (76 per cent) RER+ and 19/35 (5 4 per cent) RER - tumours showed overexpression of p53, a non-signific ant difference (chi(2) test), Although some previous studies have sugg ested differences in the clinico-pathological features and p53 express ion of RER+ and RER - right-sided CRCs, our results show that these di fferences do not exist in left-sided cancers.