The differentiation of true adenomas from colitis-associated dysplasia in ulcerative colitis: A comparative immunohistochemical study

Adenomas in areas involved by ulcerative colitis (UCA) are difficult to ide ntify because of their morphological similarity to ulcerative colitis-assoc iated dysplasia (UCD) and have an uncertain biology. Recently, a set of mor phopathologic criteria were published for the diagnosis of UCA versus UCD. As a first step to analyze these criteria, we studied p53 and bcl-2 express ion in groups of UCA and UCD along with a sporadic adenoma control group. N inety lesions from UC areas (62 patients) were examined, including 24 UCA w ithout high-grade dysplasia (HGD) and 66 UCD consisting of 43 polypoid and 23 flat dysplastic lesions (29 with HGD). Immunohistochemical p53 and bcl-2 expression were evaluated semiquantitatively. P53-positive cases were sign ificantly less frequent in the UCA (4%) versus the UCD group (30%, P = .01) and the polypoid UCD subgroup (35%, P = .005). Moderate or strong bcl-2 ex pression was significantly more frequent in the UCA than in the UCD group ( 96% v 70%, P = .01) and in the UCLA versus both polypoid and flat UCD subgr oups. Comparison of UCA with low-grade dysplastic polypoid UCD cases alone showed a difference just below significance for p53 (P = .07). p53 and bcl- 2 expression rates were very similar in the UCA group and the sporadic aden oma (n = 25) control group. These results show that UCA has phenotypic feat ures more similar to sporadic adenomas than UCD and supports the concept th at adenomas in UC have a biology different from UC-associated dysplasia. (C ) 1999 by W.B. Saunders Company.