Recent updates and debates on basal crypt dysplasia, serrated epithelial change, and p53 immunostaining in inflammatory bowel disease.

Early detection of dysplasia, followed by endoscopic or surgical resection, remains the cornerstone of colorectal cancer (CRC) prevention in patients with inflammatory bowel disease (IBD). Most dysplastic lesions in IBD resemble sporadic adenomas and pose little diagnostic difficulty, but several distinct morphologic patterns (collectively termed "nonconventional dysplasia") have recently been described. Among these, basal crypt dysplasia presents particular diagnostic challenges, as it is characterized by mild atypia confined to the crypt bases without surface involvement, contrasting with the traditional expectation that dysplasia involves both crypts and surface epithelium. Identification of basal crypt dysplasia is crucial because it typically appears as invisible or flat dysplasia, is frequently associated with synchronous and/or metachronous neoplasia, and is considered a high-risk marker for subsequent advanced neoplasia. Serrated epithelial change (SEC) represents another controversial entity in IBD. Often defined as hyperplastic polyp-like mucosal changes detected on random or non-targeted colon biopsies, SEC has been linked to synchronous/metachronous neoplasia, including invisible/flat dysplasia, nonconventional dysplasia, and advanced neoplasia, which is often found adjacent to or within the same colonic segment as SEC. Ancillary studies, such as p53 immunohistochemistry, can assist in diagnosing dysplasia, including basal crypt dysplasia and subtle dysplasia associated with SEC. This review summarizes the morphologic criteria, clinicopathologic features, and recommended reporting practices for basal crypt dysplasia and SEC, and highlights the diagnostic utility of p53 immunohistochemistry in identifying dysplasia.