Nonconventional dysplasia in ulcerative colitis: a clinicopathological study of 694 patients

Ulcerative colitis (UC) carries an increased risk of colorectal carcinoma (CRC) through the inflammation-dysplasia-carcinoma sequence. Recently, several nonconventional dysplastic subtypes have been recognized, often lacking classical features and posing diagnostic challenges.

This retrospective study evaluated dysplasia frequency and patterns in UC patients using archival colonoscopic biopsy specimens from the Pathology Laboratory at Ain Shams University Hospitals between 2020 and 2024.

A total of 694 patients with histologically confirmed UC were included. For each patient, 1 representative colonoscopic biopsy was evaluated: the most recent biopsy from the most distal colonic site when multiple biopsies were available. This specimen was reviewed histologically, regardless of whether dysplasia had previously or concurrently been diagnosed at another site. Based on this standardized approach, 203 of the 694 patients (29.3%) were found to have dysplasia, including 88 patients (43.3%) with conventional dysplasia and 115 patients (56.7%) with nonconventional dysplasia. The most common nonconventional subtype was dysplasia with increased Paneth cell differentiation (48.7%), followed by hypermucinous dysplasia (19.1%), crypt cell dysplasia (18.3%), goblet cell-deficient dysplasia (11.3%), and serrated dysplasia variants (2.6%). Over 87% of nonconventional dysplastic lesions presented endoscopically with flat/invisible appearance; however, serrated dysplasia subtypes represented an exception, as all serrated lesions in our cohort were polypoid. Patients with nonconventional dysplasia were significantly younger (median 29.5 vs. 35 years for conventional dysplasia, P=0.015).

Nonconventional dysplasia is frequent in UC, and often presents endoscopically with flat/invisible appearance. Pathologists should recognize and report these subtypes to improve surveillance accuracy.