Ampullary cancer arises from the ampulla of Vater. The ampulla of Vater is a small projection into the duodenum (the first portion of the intestine) into which the pancreatic and bile ducts open. All pancreatic and biliary secretions enter the duodenum through the ampulla of Vater.
Blockage of the ampulla of Vater by a tumor stops the drainage of pancreatic and biliary secretions into the intestine. When bile cannot drain into the intestine, it accumulates in the bloodstream, which in turn can lead to jaundice and yellowing of the skin.