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 diagnosi s and grading of ulcerative colitis-related dysplasia. Methods and results: Location Ki67 staining and location and intensity of p 53 staining were assessed in ulcerative colitis (UC) cases showing the feat ures of high-grade dysplasia (HGD, n = 14), low-grade dysplasia (LGD, n = 2 2), 'indefinite for dysplasia' (n = 12), or regenerative atypia (RA, n = 22 ). Good intra- and inter-observer reproducibilities were demonstrated in th e performance of these assessments. All the dysplasia cases showed extensio n of Ki67 staining above the basal third of the crypt. Moderate intensity p 53 staining was seen in 10/22 RA cases, but strong intensity p53 staining w as seen only in cases of dysplasia. All the cases of HGD showed extension o f Ki67 and p53 staining above the basal two thirds of the crypt. Conclusions: Restriction of Ki67 staining to the basal third of the crypt a ppears to exclude a diagnosis of dysplasia whereas strong intensity p53 sta ining suggests a diagnosis of dysplasia. Restriction of Ki67 or p53 stainin g to the basal two-thirds of the crypt appears to exclude a diagnosis of HG D.