IgG4関連硬化性胆管炎・自己免疫性膵炎・重症筋無力症に合併した胆管内乳頭状腫瘍の1例

: In the course of treatment for myasthenia gravis, enlargement of a cystic mass in the liver with peripheral bile duct dilation, diffuse pancreatic enlargement, and serum IgG4 level elevation was identified in a 65-year-old man. Following the diagnosis of autoimmune pancreatitis, a left hepatectomy was performed because of suspected malignancy of the cystic lesion. Analysis of the resected specimen revealed the cystic lesion to be a dilated bile duct. Intraductal papillary tumor comprising fibrovascular stalks covered by neoplastic epithelium was identified in the lesion. Infiltration of IgG4-positive plasma cells was discovered around the cystic lesion. Finally, a diagnosis of intraductal papillary neoplasm of bile duct with IgG4-related sclerosing cholangitis was made. Autoimmune diseases, including IgG4-related diseases, require careful observation because of their potential for malignancy.