Ampullary adenoma

by Jason Wasserman MD PhD FRCPC and Jordan Sim MD FRCPC
August 21, 2024

Background:

An ampullary adenoma is a non-cancerous growth that forms in the ampulla of Vater. The ampulla is a small opening where the bile and pancreatic ducts meet and empty their fluids into a part of the small intestine called the duodenum. These fluids help break down food during digestion. While an adenoma is benign (noncancerous), it has the potential to turn into cancer if not treated.

What are the symptoms of an ampullary adenoma?

People with an ampullary adenoma may experience symptoms like abdominal pain, jaundice (yellowing of the skin or eyes), nausea, vomiting, or unintentional weight loss if the adenoma is large enough to block the bile or pancreatic ducts. Some patients may have no symptoms, and the adenoma may be found during a test for another condition.

What causes an ampullary adenoma?

The exact cause of ampullary adenomas is not always clear. They may be related to changes (mutations) in specific genes that cause abnormal cell growth. Some people are more at risk of developing these growths due to genetic conditions.

What syndromes are associated with ampullary adenomas?

Ampullary adenomas may be associated with a genetic condition called familial adenomatous polyposis (FAP). This condition causes hundreds to thousands of polyps (small growths) to form in the colon and other parts of the digestive system, including the ampulla. These polyps have a higher risk of turning into cancer if left untreated.

How is the diagnosis of ampullary adenoma made?

The diagnosis of ampullary adenoma is usually made through imaging tests, such as an endoscopy or MRI, and a biopsy. During an endoscopy, a flexible tube with a camera is passed into the small intestine, allowing the doctor to see the adenoma and take a small tissue sample. This sample is examined under a microscope to confirm the diagnosis.

Histologic types of ampullary adenoma

Ampullary adenomas can be divided into two main types: intestinal and pancreatobiliary. Each type has different microscopic features and carries different risks.

• Intestinal type ampullary adenoma: This type of adenoma resembles the lining of the small intestine when looked at under the microscope. It usually has finger-like projections called villi. The risk of this type turning into cancer is generally lower compared to the pancreatobiliary type.
• Pancreatobiliary type ampullary adenoma: This type looks more like the lining of the pancreas or bile ducts under the microscope. It tends to have more gland-like structures. The risk of this type becoming cancer is higher, so identifying the type is important. If the adenoma is of the pancreatobiliary type, doctors may recommend closer monitoring or more aggressive treatment to prevent cancer.

What does dysplasia mean?

Dysplasia refers to abnormal changes in the cells of the adenoma. Based on how abnormal the cells look under a microscope, they can be classified as low grade or high grade.

• Ampullary adenoma with low grade dysplasia: In low grade dysplasia, the cells are hyperchromatic (darker) and the nuclei are larger and longer than normal. The risk of these cells turning into cancer is relatively low.
• Ampullary adenoma with high grade dysplasia: In high grade dysplasia, the cells are more abnormal and form irregular-shaped and closely spaced glands. The risk of an adenoma with high grade dysplasia turning into cancer is high, and whenever possible, the entire adenoma should be removed.

What is the risk that an ampullary adenoma will turn into cancer?

The risk that an ampullary adenoma will turn into cancer depends on its histologic type. Intestinal type adenomas carry a lower risk of transformation into cancer, but that risk still exists, especially in cases with high grade dysplasia. On the other hand, pancreatobiliary type adenomas have a much higher risk of developing into cancer, which is why these adenomas often require more careful monitoring and may prompt earlier intervention.

Complete resection, or removal, of the adenoma is the best way to reduce the risk of cancer. By removing the entire adenoma, doctors can help prevent any remaining abnormal cells from progressing to cancer. This is especially important for adenomas with high grade dysplasia or those of the pancreatobiliary type, where the cancer risk is significantly higher. Regular follow-up is also important to monitor for any recurrence or new growths.