colorectal cancer
colorectal cancer
OVERVIEW
Colorectal cancer develops in the colon or rectum. Depending on where they begin, these cancers are also known as colon cancer or rectal cancer. Because they share many characteristics, colon cancer and rectal cancer are frequently lumped together.
The colon and rectum
Understanding colorectal cancer requires knowledge of the normal structure and function of the colon and rectum.
The large intestine (or large bowel) is made up of the colon and rectum and is part of the digestive system, also known as the gastrointestinal (GI) system.
The colon, a muscular tube about 5 feet (1.5 metres) long, makes up the majority of the large intestine. The parts of the colon are named after the direction in which food passes through them.
How do the colon and rectum work?
After passing through the small intestine, the colon absorbs water and salt from the remaining food matter (small bowel). The waste matter that remains after passing through the colon is deposited in the rectum, the last 6 inches (15cm) of the digestive system.
It is kept there until it is processed by the anus. Ring-shaped muscles (also known as sphincters) surround the anus and prevent stool from exiting until they relax during a bowel movement.
How does colorectal cancer start?
The majority of colorectal cancers begin as a growth on the lining of the colon or rectum. Polyps are the medical term for these growths.
Some polyps can develop into cancer over time (usually many years), but not all polyps do. The likelihood of a polyp developing into cancer is determined by the type of polyp. Polyps come in a variety of shapes and sizes.
- Adenomatous polyps (adenomas): These polyps can develop into cancer. As a result, adenomas are classified as a pre-cancerous condition. Adenomas are classified into three types: tubular, villous, and tubulovillous.
- Hyperplastic polyps and inflammatory polyps: These polyps are more common, but they are not pre-cancerous in most cases. Some people with large (more than 1cm) hyperplastic polyps may require more frequent colorectal cancer screening with a colonoscopy.
- Sessile serrated polyps (SSP) and traditional serrated adenomas (TSA): Because of their increased risk of colorectal cancer, these polyps are frequently treated as adenomas.
How colorectal cancer spreads
If cancer develops in a polyp, it has the potential to spread to the colon or rectum wall over time. The colon and rectum’s walls are made up of many layers.
Colorectal cancer begins in the innermost layer (the mucosa) and can spread to any or all of the other layers.
When cancer cells become embedded in the wall, they can develop into blood vessels or lymph vessels (tiny channels that carry away waste and fluid). They can then spread to nearby lymph nodes or to distant parts of the body.
A colorectal cancer’s stage (the extent to which it has spread) is determined by how deeply it has grown into the wall and whether it has spread outside the colon or rectum.
Types of cancer in the colon and rectum
The majority of colorectal cancers are adenocarcinomas. These cancers begin in cells that produce mucus to lubricate the colon and rectum. When doctors discuss colorectal cancer, they almost always refer to this type. Some subtypes of adenocarcinoma, such as signet ring and mucinous, may have a poorer prognosis (outlook) than others.
Less common types of tumors
Other, much rarer types of tumours can also begin in the colon and rectum. These are some examples:
- Carcinoid tumours These are produced by special hormone-producing cells in the intestine.
- Gastrointestinal stromal tumours (GISTs) develop from interstitial cells of Cajal, which are found in the colon’s wall. Some are harmless (not cancer). These tumours can occur anywhere in the digestive tract, but they are uncommon in the colon.
- Lymphomas are cancers of the immune system. They typically begin in the lymph nodes, but they can also begin in the colon, rectum, or other organs.
- Sarcomas can develop in blood vessels, muscle layers, or other connective tissues in the colon and rectum wall. Colon or rectum sarcomas are uncommon.
My locations
I can offer consultations in several locations across Mauritius. Some of them are: