Pyloric gland metaplasia with perineural invasion of the gallbladder: A lesion that can be confused with adenocarcinoma

BACKGROUND: Metaplastic pyloric glands have been described in a variety of organs including the gallbladder, in which they can extend into the muscular wall and serosa. METHODS: Clinical, histologic, and immunohistochemical features of four cases of gallbladder florid pyloric gland metaplasia with perineural and intraneural invasion are analyzed. RESULTS: The patients with pyloric gland metaplasia and perineural and intraneural invasion were all females ages 57-72 years. A preoperative diagnosis of chronic cholecystitis and cholelithiasis was made for all four patients, but a histologic diagnosis of adenocarcinoma was made for two patients and entertained in two others. Macroscopically the gallbladders showed changes usually associated with chronic cholecystitis. No intraluminal masses were observed in any of the gallbladders. The characteristic microscopic features included florid pyloric gland metaplasia, proliferation of medium-sized nerve trunks more prominent in the muscular layer and serosa, and perineural and intraneural invasion by the metaplastic glands lined by cytologically bland cuboidal or columnar mucin-containing cells. At last follow-up all patients were alive and symptom free 1-7 years after laparoscopic cholecystectomy. CONCLUSIONS: Pyloric gland metaplasia of the gallbladder should be added to the long and increasing list of benign epithelial proliferations that are associated with perineural and intraneural invasion. This lesion should not be mistaken for adenocarcinoma of the gallbladder, a misinterpretation that may have serious therapeutic implications. The pathogenesis of this phenomenon is unknown.