Carcinomas of the pancreas, gallbladder, extrahepatic bile ducts, and ampulla of vater share a field for carcinogenesis: a population-based study.

CONTEXT: Carcinomas co-occur in the pancreas, extrahepatic bile ducts, and ampulla of Vater. We investigated whether cancers originating in these sites represent a field effect similar to that observed in the lung and upper aerodigestive tract.
OBJECTIVE: To determine whether a field effect for carcinogenesis exists in the ampulla of Vater, extrahepatic bile ducts, gallbladder, and pancreas.
DESIGN: Data were obtained from National Cancer Institute's Surveillance Epidemiology and End Results Program from 1973 through 2005. Cases were compared by age frequency density plots, age-specific incidence rates, and logarithmic plots of the age-specific incidence rates and age of diagnosis.
RESULTS: Incidence rates were 11.71, 1.43, 0.88, and 0.49 per 100,000 persons at risk for pancreatic, gallbladder, extrahepatic bile ducts, and ampullary carcinomas, respectively. Age frequency density plots were congruent for cancers originating in all 4 sites. Logarithmic plots of the age-specific incidence rates with age of diagnosis produced parallel linear rate patterns for the 4 sites indicative of similar populations for tumor development. However, density and logarithmic plots of pancreatic endocrine carcinomas, a tumor of different cellular differentiation and carcinogenic pathway, served as a comparison. The endocrine carcinomas showed a different age distribution and nonparallel rate patterns with ductal carcinomas.
CONCLUSIONS: Carcinomas of the pancreas, gallbladder, extrahepatic bile ducts, and ampulla have a common embryonic cellular ancestry, differentiation pathways, mucosal histologic patterns, and population-related tumor development indicating a field effect in carcinogenesis. Parallel linear rate patterns indicate (1) the rate of cancer development is similar in all 4 sites even though the absolute incidence rates vary and (2) regardless of location, the ductal epithelium is equally susceptible to malignant transformation. If carcinogenic pathways to cancer are similar, then the different incidence rates seen clinically may depend on the relative surface area of the ductal system in these sites. Pancreatic cancers are most common because the surface area of the pancreas' ductal system is greater than that of the gallbladder, extrahepatic bile ducts, and ampulla.