COMPARISON OF P53 GENE MUTATION AND PROTEIN OVEREXPRESSION IN COLORECTAL CARCINOMAS

Immunocytochemistry (ICC) has been used routinely to stain for p53 ove rexpression in a range of human tumours. The underlying assumption has been that positive staining indicates a mutation in the p53 coding se quence. Recently, however, discordancy has been observed and the accur acy of ICC as a marker of p53 gene mutation has been questioned. In th is study of 109 colorectal adenocarcinomas, we compared ICC staining w ith p53 gene mutations detected by single-strand conformation polymorp hism (SSCP) analysis. Concordancy between the two techniques was found in 69% of tumours. ICC-positive/SSCP-negative cases accounted for 20% of rumours and ICC-negative/SSCP-positive cases for the remaining 11% . These results caution against the assumption that p53 protein overex pression is always associated with a gene mutation. Epigenetic phenome na may account for a significant proportion of ICC-positive tumours.