An immunohistochemical study of p53 protein in gallbladder and extrahepatic bile duct/ampullary carcinomas.

BACKGROUND: p53 mutations are known to occur frequently in human cancers, including gallbladder carcinoma. However, there has been no study of p53 expression in extrahepatic bile duct/ampullary carcinoma. Furthermore, gallbladder carcinoma is associated with cholelithiasis, whereas no such association is known for extrahepatic bile duct carcinoma, suggesting that they could arise from different pathogenetic mechanisms.
METHODS: Twenty-four gallbladder carcinomas and 35 extrahepatic bile duct/ampullary carcinomas were stained with an anti-human p53 protein monoclonal antibody by the streptavidin-biotin immunoperoxidase method. Both the extent and intensity of p53 protein staining were noted.
RESULTS: Ninety-two percent of the gallbladder carcinomas stained for p53 protein compared with only 66% of the extrahepatic bile duct/ampullary carcinomas. The statistical significance was maintained even when the comparison was restricted to strong p53 staining in moderately to poorly differentiated adenocarcinomas (P < 0.05). Of the gallbladder carcinomas, poorly differentiated adenocarcinomas stained more strongly than well to moderately differentiated adenocarcinomas; the converse was true for extrahepatic bile duct/ampullary adenocarcinomas.
CONCLUSION: The majority of gallbladder and extrahepatic bile duct/ampullary carcinomas stain for p53 protein. The incidence and pattern of staining is different, however, and supports the contention that these could be different tumors with differing etiologies and pathogenetic mechanisms.