Morphology and genetics of pyloric gland adenomas in familial adenomatous polyposis

Aims Gastric pyloric gland adenomas ( PGA s) are rare epithelial polyps that are found more commonly in autoimmune atrophic gastritis and familial adenomatous polyposis (FAP). Little is known about the morphology and genetics of PGA s in FAP . PGA s in FAP are studied morphologically and genetically. Findings in FAP ‐associated PGA s are compared to sporadic PGA s and related lesions such as oxyntic gland adenoma ( OGA ) to increase our understanding of these rare polyps. Methods and results Seven PGA s and 18 fundic gland polyps ( FGP s) from FAP patients were collected. KRAS and GNAS mutations were determined in six PGA s and 18 FGP s. Immunohistochemistry was applied on five PGA s to provide further confirmation of the histological subtypes and genetic alterations. Morphology of all PGA s was studied and compared to literature on sporadic PGA s and related lesions. All successfully sequenced PGA s (six of six) carried GNAS mutations and half of the successfully sequenced PGA s carried a KRAS mutation (three of six). Nuclear β‐catenin was seen only in one PGA with focal high‐grade dysplasia. Morphologically, PGA s in FAP showed overlapping features with OGA . Conclusion Familial adenomatous polyposis‐associated PGA s have a similar genetic background as sporadic PGA s, i.e. KRAS and GNAS mutation. Based on morphological findings in FAP associated PGA s, it is hypothesized that PGA s and OGA s are closely related lesions.