Inflammatory bowel disease-related neoplasia is broadly classified as elevated dysplasia and flat dysplasia. Elevated lesions, or dysplasia-associated lesions or masses (DALMs), are further subclassified based on their resemblance, or lack thereof, to colonic adenomas (Figure 15.1). Adenoma-like DALMs are circumscribed lesions, similar to sporadic colorectal adenomas. Nonadenoma-like DALMs appear as plaques, strictures, or ill-defined, broad-based nodules. Flat dysplasia is much less common, accounting for less than 5% of inflammatory bowel disease-related dysplasias. It is, by definition, endoscopically inapparent and discovered by random surveillance biopsies.⁴

Both raised and flat dysplasias are histologically classified as low or high grade using criteria that parallel those applied to sporadic adenomas, as discussed in Chapter 4. Briefly, low-grade dysplasia shows crypts lined by epithelial cells with elongated, hyperchromatic, pseudostratified nuclei that do not mature at the luminal surface (Figure 15.2A). High-grade dysplasia contains cell with round, stratified nuclei that show severe atypia and contain prominent nucleoli. Most high-grade dysplasias also display architectural complexity with cribriform and interanastomosing glands (Figure 15.2B). Lesions that show some degree of cytologic atypia but do not meet criteria for low-grade dysplasia may be classified as indefinite for dysplasia. This situation is typically encountered when cytologic atypia is present in the crypts, but not the surface epithelium, or when cytologic changes resembling those of dysplasia occur in combination with active inflammation (Figure 15.3).

Accurate gross and histologic classification of inflammatory bowel disease-associated dysplasia is important because treatment recommendations vary depending on the endoscopic appearance of the lesion and severity of dysplasia (Figure 15.4). The natural history of low-grade dysplasia in inflammatory bowel disease is variable; 5% to 50% of cases are associated with cancer development.⁵,⁶ Unifocal low-grade dysplasia in nonadenoma-like DALMs or flat mucosa may be managed with either surveillance colonoscopy or proctocolectomy. Multifocal non adenoma-like DALMS and flat dysplasia are indications for colectomy owing to the high incidence of synchronous and metachronous adenocarcinoma in these situations.² In contrast to flat dysplasia and nonadenoma-like DALMs, adenoma-like DALMs can be managed with complete endoscopic resection, similarly to sporadic adenomas, irrespective of dysplasia grade.⁷ Patients with adenoma-like DALMs are followed according to standard surveillance guidelines, provided that biopsies of the surrounding mucosa are negative for dysplasia and no dysplasia is found elsewhere in the colon.⁴

Surveillance of patients with inflammatory bowel disease is largely performed using white light (conventional) colonoscopy. Most colonoscopes contain magnifying lenses that enlarge white light images up to 150 times and reveal distinct patterns of surface colonic crypt openings that correlate with the presence of histologic dysplasia (Figure 15.5).¹⁰ Unfortunately, white light fails to detect a substantial number of colitis-associated dysplasias.² Other endoscopic techniques have been recently developed with the hope to increase the sensitivity and specificity of endoscopic evaluation but decrease the number of biopsies required for dysplasia detection. These techniques are broadly grouped into chromoendoscopic methods and optical biopsy technologies, as discussed further below.