Pancreatic Cancer: Classifications
Tumors that appear to be of exocrine or endocrine type are diagnosed and treated in very different ways.
The majority of cells in the pancreas are exocrine cells and over 90% of pancreatic tumors are referred to as ductal adenocarcinomas, made up of abnormal cells that arise in the lining of the pancreatic duct. Most of them are found near the head of the pancreas, closest to the duodenum and the bile ducts. Then they may spread to nearby organs – such as the bile duct, intestine, or stomach – or to adjacent blood vessels. Abnormal cells can also spread to the nearby lymph nodes or into the bloodstream and deposit in the liver or other organs. Since the tumors in the head of the pancreas often block the bile ducts many patients show signs of jaundice, a yellowing of the skin and eyes and this may lead to detection before the tumor has spread.
Another less common type of cancer—ampullary cancer—originates where the bile duct (coming from the liver) and the pancreatic duct meet and drain into the small intestine. These tumors may also lead to jaundice but are usually less aggressive than pancreatic tumors .Though they are not technically considered pancreatic cancer, many aspects of the treatment of ampullary cancers is similar to pancreatic tumors.
Tumors of the endocrine gland account for fewer than 5 percent of pancreatic cancers. These are known as islet cell tumors or neuroendocrine tumors.
Pancreatic neuroendocrine tumors, or PNETS, are treated differently than pancreatic adenocarcinomas. They are sensitive to drugs which block blood vessel formation and also to different classes of chemotherapy, particularly alkylating agents. They usually have a better prognosis than adenocarcinomas. It is important to have expert pathologic review to confirm the type of pancreatic cancer for these reasons.