From Adenoma to Carcinoma, Why Screening Matters

The purpose of this article is to educate patients regarding colon cancer screening for the detection of adenomatous polyps or adenomas. These polyps can generally be considered precursors to colon cancer, the third most common type of cancer diagnosed in both men and women in the United States. As a pathologist who analyzes tissue under a microscope, I directly appreciate the benefits of screening colonoscopy in the prevention and early detection of colon cancer.

So what is an adenomatous polyp?

An adenomatous polyp, or adenoma, is a benign tumor that makes glands (the same glands that line the colon). Adenomatous polyps are thought to give rise to cancer through what is known as the adenoma-carcinoma sequence.

What is a carcinoma?

In the context of colon cancer, the appropriate term is adenocarcinoma, which is a malignant tumor that makes glands. Malignant tumors, by definition, invade tissues (in this case the wall of the colon) and have the capacity to spread to other organs (metastasize) by way of blood vessels.

What is the adenoma-carcinoma sequence?

This is a sequence of genetic alterations that leads to the development of cancer- beginning with the development of an adenoma, which progresses to an adenocarcinoma.

Is there something you can do to prevent the adenoma-carcinoma sequence from occurring?

In other words, what things can be done to reduce the risk of developing colon cancer? It is thought that the progression from an adenoma to a carcinoma takes 10-15 years and that this process occurs most commonly after the age of 50. For this reason, colon cancer screening guidelines recommend colonoscopy, and other screening methods, beginning at that age. The purpose of colon cancer screening is to detect and remove polyps or to detect colonic adenocarcinoma at an early stage – before it spreads. For individuals who have a family history, genetic predisposition or other conditions which may lead to the development of colon cancer at a younger age, screening may be recommended earlier.

While the adenoma-carcinoma sequence describes a series of genetic abnormalities leading to cancer, environmental factors such as diet and other lifestyle characteristics are thought to play an important contributing role in the development colon cancer. The so-called “Western” diet, characterized by high intakes of red and processed meats, refined grains and sweets is thought to contribute to the relatively increased incidence of colon cancer in the United States. On the other hand, a diet high in fruits, vegetables, poultry, and fish may lower the risk for the development of the same disease.

In conclusion, colon cancer is thought to develop from precursor lesions (adenomatous polyps) that can be detected early and removed through screening colonoscopy. Other factors to consider include your individual risk, particularly family history, and maintaining a healthy lifestyle, which includes diet and exercise. Each individual should discuss the most appropriate screening strategy with their physician.