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Endoscopic transpapillary biopsy (ETPB) of human extrahepatic bile ducts--light and electron microscopic findings, clinical significance.

Endoscopic transpapillary biopsy (ETPB) has been performed in 106 patients to investigate the fine structure of human bile ducts, and to assess its clinical significance. Three hundred and twenty-six biopsy specimens obtained from the hepatic and common bile duct and from the ampullary/papillary region were examined by light, transmission and scanning electron microscopy. No complications due to biopsy occurred. The epithelium lining at the bile duct contains 5 different types of cells: the main epithelial cell, endocrine/paracrine cells, tuft cells, immunocompetent cells and goblet cells. Twenty-one ampullary carcinomas, and 26 benign neoplastic ampullary lesions were diagnosed. In 8 of the former, only second-look, follow-up biopsies established the presence of a carcinoma. While the clinical significance of "blind" hepatic duct biopsy is not readily apparent, ETPB is the diagnostic method of choice for ampullary neoplasms, and extensive biopsies from even tiny ampullary lesions are mandatory.