Imaging manifestations of malignancy in inflammatory bowel disease: patterns, pitfalls and pearls

Patients with inflammatory bowel disease (IBD) are at increased risk of gastrointestinal and hepatobiliary malignancies arising in the setting of chronic inflammation, dysplasia, stricturing disease, and fistulizing complications. Although endoscopic surveillance remains the cornerstone for dysplasia detection, imaging plays an increasingly important complementary role in identifying invasive malignancy, evaluating transmural and extra-intestinal disease, and detecting lesions in segments inaccessible or poorly amenable to endoscopic assessment. Distinguishing malignant transformation from chronic inflammatory change remains challenging because imaging findings frequently overlap. In practice, malignancy is often suggested less by a single defining feature than by deviation from the expected imaging behaviour of inflammatory disease over time. This review summarizes the imaging manifestations of malignancy in IBD across the small bowel, colon, rectum, perianal region, and hepatobiliary system, with emphasis on Crohn's disease-associated small bowel adenocarcinoma, colitis-associated colorectal carcinoma, fistula-associated anorectal malignancy, and cholangiocarcinoma in primary sclerosing cholangitis. Key diagnostic pitfalls, mimics, and structured reporting considerations are discussed, together with emerging quantitative and molecular imaging techniques including diffusion-weighted MRI, dual-energy CT, radiomics, elastography, and fibroblast activation protein inhibitor (FAPI)-based imaging. Recognition of subtle interval morphologic change and discordance from expected inflammatory behaviour is central to earlier detection of IBD-associated malignancy. Careful longitudinal comparison and multidisciplinary correlation remain essential, with radiologists playing a critical role in identifying imaging features that warrant intensified surveillance, tissue sampling, or further intervention.