Preinvasive neoplasia of the gallbladder: flat and tumoral dysplasia

Abstract

Gallbladders are one of the most commonly encountered specimens in routine histopathology. While the usual diagnoses of cholelithiasis and cholecystitis are relatively straightforward, the evaluation of neoplastic changes in the gallbladder can be challenging. Non-invasive neoplasia in the gallbladder can be broadly categorised into flat or non-tumoral dysplasia and tumoral dysplasia, the latter mainly incorporating intracholecystic papillary neoplasms, akin to lesions seen within the bile ducts and pancreas. Flat dysplasia can be particularly difficult to diagnose due to morphological overlaps with reactive atypia, compounded by the common presence of inflammatory changes in cholecystectomy specimens. Tumoral dysplasia, while more easily recognisable, can be problematic due to the different, clinically relevant subtypes that exist. These display variable associations with invasive malignancy and the morphological differences between these lesions can be subtle. This review provides an overview of the key features of flat and tumoral dysplasia in the gallbladder, an approach to handling such cases, and some insights into the main diagnostic challenges that may be faced by general histopathologists when a neoplastic diagnosis is being considered.