by Jason Wasserman MD PhD FRCPC
February 1, 2023
A nonampullary duodenal adenoma is a non-cancerous type of polyp that starts in a part of the small intestine called the duodenum. It is considered a precancerous condition because it can turn into a type of cancer called adenocarcinoma over time.
This type of adenoma is described as “nonampullary” when it is found in a part of the duodenum away from a structure called the ampulla. The ampulla (also known as the ampulla of Vater) is a small opening that connects the common bile duct and the main pancreatic duct to the duodenum. It is through the ampulla that bile (from the gallbladder) and secretions (from the pancreas) flow into the duodenum.
Just over half of all nonampullary duodenal adenomas occur in patients with familial adenomatous polyposis (FAP) syndrome. In these patients, adenomas are caused by an APC gene mutation leading to increased cell growth and division. Just under half of all nonampullary duodenal adenomas occur in patients without FAP and at present doctors do not know what causes these adenomas to develop.
Small nonampullary duodenal adenomas do not cause any symptoms and are usually found incidentally when an examination called an upper endoscopy is performed. Larger adenomas that block the duodenum can cause symptoms such as abdominal pain, bloating, vomiting, and nausea.
Nonampullary duodenal adenomas are uncommon, being found in less than 1% of people examined by upper endoscopy. However, the rate is much higher in patients with FAP.
All nonampullary duodenal adenomas show an abnormal pattern of growth called dysplasia. Dysplasia is important because it is a precancerous change that can become cancerous over time. When examining a nonampullary duodenal adenoma, pathologists divide dysplasia into two levels – low grade dysplasia and high grade dysplasia.
Low grade dysplasia is an early precancerous change seen in most nonampullary duodenal adenomas. If left untreated, low grade dysplasia can change into high grade dysplasia or cancer over time. However, the overall risk is low.
High grade dysplasia is a more advanced precancerous change seen in a small number of nonampullary duodenal adenomas. If left untreated, nonampullary duodenal adenomas with high grade dysplasia can turn into a type of cancer called adenocarcinoma. If possible, all nonampullary duodenal adenomas with high grade dysplasia should be removed completely.
The diagnosis of nonampullary duodenal adenoma can only be made after part, or all of the adenoma is removed and the tissue is examined under the microscope by a pathologist.