Gastrointestinal cancers in inflammatory bowel disease: An update with emphasis on imaging findings

Inflammatory bowel diseases (IBD) are associated with an increased risk of gastrointestinal cancers depending on the specific type of IBD, the extent of the disease and its location. Patients with IBD and extensive colonic involvement are at increased risk of colorectal cancer whereas patients with Crohn disease have an increased risk for small-bowel and anal carcinoma. These cancers preferentially develop on sites of longstanding inflammation. In regards to colon cancer, several key pathogenic events are involved, including chromosomal instability, microsatellite instability and hypermethylation. The risk for colon cancer in IBD patients correlates with longer disease duration, presence of sclerosing cholangitis, pancolitis, family history of colorectal cancer, early onset of the disease and severity of bowel inflammation. Identification of increased colorectal cancer risk in individual IBD patients has led to formal surveillance guidelines. Conversely, although an increased risk for other types of cancer has been well identified, no specific formal screening recommendations exist. Consequently, the role of the radiologist is crucial to alert the referring gastroenterologist when a patient with IBD presents with unusual imaging findings at either computed tomography (CT) or magnetic resonance (MR) imaging. This review provides an update on demographics, molecular, clinical and histopathological features of gastrointestinal cancers in IBD patients including colorectal carcinoma, small bowel adenocarcinoma, neuroendocrine tumors and anal carcinoma, along with a special emphasis on the current role of CT and MR imaging.