Non‐conventional dysplasias of the tubular gut: a review and illustration of their histomorphological spectrum

Abstract

Non-conventional dysplasias of the tubular gut: a review and illustration of their histomorphological spectrumThe increasing use of gastrointestinal endoscopic procedures has led to the recognition by histopathologists of non-conventional (or special-type) dysplasias of the gastrointestinal tract. These lesions can be recognised in association with prevalent underlying gastrointestinal conditions, such as Barrett oesophagus, chronic atrophic gastritis, and inflammatory bowel disease. The diagnosis of these special types can be challenging, and their biological behaviours are not fully characterised. The aim of this review is to provide a global view of non-conventional dysplastic lesions observed in the various segments of the tubular gastrointestinal tract and describe their salient features. Furthermore, as the clinical implications of these various subtypes have not been broadly tested in practice and are not represented in most management guidelines, we offer guidance on the best management practices for these lesions.

Non-conventional dysplastic subtypes in inflammatory bowel disease: a review of their diagnostic characteristics and potential clinical implications

“…Although pathologists have a good grasp of the morphologic criteria of conventional dysplasia, several unfamiliar morphologic patterns of dysplasia (collectively known as "non-conventional" dysplasia) have been recently described in IBD. There are at least seven subtypes, including (1) hypermucinous dysplasia; (2) crypt cell dysplasia; (3) dysplasia with increased Paneth cell differentiation; (4) goblet cell deficient dysplasia; (5) SSL-like dysplasia; (6) TSA-like dysplasia; and (7) serrated dysplasia NOS [38,[41][42][43]. Although their clinicopathologic and molecular features are not fully characterized, in part due to the rarity of these subtypes and the likelihood that they are under-recognized, the recognition of these non-conventional subtypes is becoming increasingly important, as they often present as invisible/flat lesions, and at least some of them appear to have a higher malignant potential than conventional dysplasia or sporadic adenomas.…”

“…Morphologically, hypermucinous dysplasia most often demonstrates a tubulovillous/villous architecture lined by tall, prominent mucinous cells representing > 50% of the lesion (Fig. 3A, B) [38,41,43]. Although low-grade dysplastic features are usually present in crypts, the degree of atypia tends to decrease towards the surface epithelium due to prominent mucinous differentiation, so one must be careful not to miss hypermucinous dysplasia when evaluating superficial fragments with hypermucinous features but without significant nuclear atypia (Fig.…”

“…Histologically, crypt cell dysplasia is characterized by mildly enlarged, round-to-oval or slightly irregular, crowded, hyperchromatic nuclei limited to the crypt base without surface involvement or significant architectural atypia (Fig. 3C, D) [38,42,43]. Increased mitoses at the base of crypts are common (Fig.…”

“…The defining histologic feature of dysplasia with increased Paneth cell differentiation is increased Paneth cell differentiation involving at least two contiguous dysplastic crypts in two different foci (beyond what is present in background mucosa) (Fig. 4A, B) [38,41,43]. It usually demonstrates a tubular architecture mostly lined by elongated, hyperchromatic nuclei involving both crypts and surface epithelial cells.…”

“…Morphologically, goblet cell deficient dysplasia is defined by a complete or near-complete absence of goblet cells, often leading to intensely eosinophilic cytoplasm (Fig. 4C, D) [38,41,43]. It predominantly shows a tubular architecture with low-grade dysplastic features involving both crypts and surface epithelial cells.…”