The term "pyloric gland
adenoma" reflects its etiogenesis from deep mucoid glands in the stomach. The diagnosis can be confirmed by immunohistochemistry. Typically, pyloric gland
adenomas are strongly positive for
Mucin 6 (deep mucoid gastric glands). These lesions express
Mucin 6 over the whole lesion up to the surface often only with a small layer of columnar epithelium expressing
Apomucin 5AC. The amount of
mucin 5AC which is expressed on normal within the apical foveolar epithelium might vary from case to case. Combination or transdifferentiation with ordinary tubular (intestinal differentiation)
adenoma can be observed. The gastric corpus mucosa of elderly female patients with autoimmune
gastritis is highly affected. The frequency of pyloric gland
adenoma is given in the literature being 2.7% of all gastric
polyps. Therefore pyloric gland
adenomas are not that rare that one might assume. Only a few publications are available which makes one think that these lesions are frequently misinterpreted. Pyloric gland
adenomas can arise in gastric heterotopia and gastric
metaplasia in the whole gastrointestinal tract. The clinical significance is given by a 30% rate of malignant transformation. These cases represent for the most well differentiated early
adenocarcinomas which are known to have an excellent prognosis after complete polypectomy and limitation to the mucosal layer.