Pathology: Non-neoplastic and Neoplastic Diseases of the Gallbladder

Pathological features of inflammatory, non-neoplastic proliferative, and neoplastic diseases of the gallbladder are described in this chapter. Inflammatory diseases of the gallbladder develop mostly in the setting of cholecystolithiasis, but the exact mechanisms underlying how gallstones cause inflammations are not yet clear. In acute cholecystitis, regardless of calculous or acalculous status, adipocytes in the subserosal layer disappear and are replaced by fibroblastic proliferation. The mucosa is also often inflamed, and some cases show transmural necrosis. Suppurative inflammation that represents infection is likely a secondary change. In contrast, a layer of nearly uniform thickness of fibrosis with minimal lymphocytic infiltration observed just beneath the lamina muscularis propria is a characteristic feature of chronic cholecystitis. Xanthogranulomatous cholecystitis and IgG4-related cholecystitis are peculiar inflammatory diseases that may simulate gallbladder carcinomas. When porcelain gallbladders are examined, pathologists must take care not to overlook co-existing carcinomas. Infarction occurs in the gallbladder in the setting of torsion or embolization. Adenomyomatosis and cholesterol polyps are representative non-neoplastic proliferative diseases in the gallbladder. Neoplastic diseases of the gallbladder are diverse, and adenocarcinoma is the most common, usually arising in the background of biliary intraepithelial neoplasia. Variants of adenocarcinoma and other types of neoplasia (e.g., squamous cell carcinoma, undifferentiated carcinoma, neuroendocrine carcinoma, mucinous carcinoma, poorly cohesive carcinoma, intracystic papillary neoplasms, and pyloric gland adenoma) also occur in the gallbladder. Controversies remain regarding the concepts of some neoplasms, but further progress in the field of molecular studies may resolve the issues.