Alpha-1-antitrypsin-positive "signet-ring" bile duct adenoma in a patient with M(MALTON) mutation.

A 65-year-old man with a colonic adenocarcinoma and a single small liver nodule underwent surgery. The nodule showed the histological features of a bile duct adenoma. Large eosinophilic, periodic acid-Schiff-positive diastase-resistant intracytoplasmic globules conferred a signet-ring appearance to the cells. Similar globules were found in the biliary epithelium in perinodular portal tracts, whereas smaller globules were detected in periportal hepatocytes. All globules showed strong immunoreactivity for alpha-1-antitrypsin, and the sequence of the alpha-1-antitrypsin gene showed a heterozygous M(malton) genotype. The selective recurrence of large alpha-1-antitrypsin globules within the bile ducts may indicate a neoplastic rather than a reactive or hamartomatous nature of the nodule.