Immunohistochemical assessment of Ki67 and p53 expression assists the diagnosis and grading of ulcerative colitis-related dysplasia

AIMS: To assess whether Ki67 and p53 immunostaining may assist the diagnosis and grading of ulcerative colitis-related dysplasia. METHODS AND RESULTS : Location of Ki67 staining and location and intensity of p53 staining were assessed in ulcerative colitis (UC) cases showing the features of high-grade dysplasia (HGD, n = 14), low-grade dysplasia (LGD, n = 22), 'indefinite for dysplasia' (n = 12), or regenerative atypia (RA, n = 22). Good intra- and inter-observer reproducibilities were demonstrated in the performance of these assessments. All the dysplasia cases showed extension of Ki67 staining above the basal third of the crypt. Moderate intensity p53 staining was seen in 10/22 RA cases, but strong intensity p53 staining was seen only in cases of dysplasia. All the cases of HGD showed extension of Ki67 and p53 staining above the basal two thirds of the crypt. CONCLUSIONS: Restriction of Ki67 staining to the basal third of the crypt appears to exclude a diagnosis of dysplasia whereas strong intensity p53 staining suggests a diagnosis of dysplasia. Restriction of Ki67 or p53 staining to the basal two-thirds of the crypt appears to exclude a diagnosis of HGD.