Figure 1.

Premalignant biliary lesions. A: Biliary intraepithelial neoplasia. Biliary epithelium with nuclear pseudostratification and atypia; B: Intraductal papillary neoplasm of the bile duct. Papillary proliferation of neoplastic cells lining thin fibrovascular cores; C: Von Meyenburg complex. Small well-circumscribed lesion consisting of dilated irregular bile ducts embedded within dense collagenous stroma; D: Bile duct adenoma. Well-circumscribed proliferation of small uniform tubules surrounded by fibrous stroma.