What Exactly Is Colorectal Cancer?
Colorectal cancer develops in the colon or rectum. Depending on where they begin, these malignancies are also known as colon cancer or rectal cancer. Because they have many characteristics, colon and rectal cancer are sometimes lumped together.
Cancer develops when cells in the body begin to proliferate uncontrollably. To find out more about how tumours begin and spread, visit
The rectum and colon
Understanding colorectal cancer requires knowledge of the normal structure and function of the colon and rectum.
The large intestine (or big bowel) is made up of the colon and rectum and is part of the digestive system, commonly known as the gastrointestinal (GI) system. (see illustration below).
The colon, a muscular tube roughly 5 feet (1.5 metres) length, makes up the majority of the large intestine. The portions of the colon are named after the direction in which food passes through them.
1 The ascending colon is the first portion. It begins with a pouch called the cecum, which receives undigested food from the small intestine. It climbs up the right side of the abdomen. (belly).
2 The second section is called the transverse colon. It goes across the body from the right to the left side.
3 The transverse colon is the name given to the second portion. It runs from the right to the left side of the body.
4 Because of its “S” form, the fourth portion is known as the sigmoid colon. The sigmoid colon links with the rectum, which connects with the anus. Because of its “S” form, the fourth portion is known as the sigmoid colon. The sigmoid colon links with the rectum, which connects with the anus.
The proximal colon is made up of the ascending and transverse parts. The distal colon includes the descending and sigmoid colons.The proximal colon is made up of the ascending and transverse parts. The distal colon includes the descending and sigmoid colons.
How do the colon and rectum function?
After passing through the small intestine, the colon absorbs water and salt from the leftover food debris. (small bowel). The waste stuff 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
What causes colorectal cancer to develop?
Polyps in the rectum or colon
The majority of colorectal cancers begin as a tumour on the lining of the colon or rectum. Polyps are the medical term for these growths.
Some polyps can develop into cancer over time (typically many years), but not all polyps do. The likelihood of a polyp developing into cancer is determined by the type of polyp. Polyps are classified into several categories.
1 Adenomatous polyps (adenomas): These polyps might develop into cancer. As a result, adenomas are classified as pre-cancerous conditions. Adenomas are classified into three types: tubular, villous, and tubulovillous.
2 Hyper-plastic and inflammatory polyps are more common, however, they are not pre-cancerous in most cases. Some persons with big (greater than 1cm) hyper-plastic polyps may require more frequent colorectal cancer screening with a colonoscopy. hyper-plastic and inflammatory polyps are more common, however, they are not pre-cancerous in most cases. Some persons with big (greater than 1 cm) hyper-plastic polyps may require more frequent colorectal cancer screening with a colonoscopy.
3 Traditional serrated adenomas (TSA) and sessile serrated polyps (SSP): Because of the increased risk of colorectal cancer, these polyps are frequently treated as adenomas.
Other factors that can enhance the likelihood of a polyp containing cancer or raise someone’s risk of having colorectal cancer include:
1 If a polyp larger than 1 cm is discovered,
2 If more than three polyps are discovered,
3 If dysplasia is discovered in the polyp after it has been resected. Another precancerous condition is dysplasia. It signifies that there is a region in a polyp or the lining of the colon or rectum where the cells appear abnormal but have not developed into cancer.
The Spread of Colorectal Cancer
If cancer develops in a polyp, it can spread to the colon or rectum wall over time. The colon and rectum walls are made up of numerous layers. Colorectal cancer begins in the innermost layer (the mucosa) and can spread to any or all of the subsequent layers. (see picture below).
Cancer cells in the wall might develop into blood vessels or lymph vessels. (tiny channels that carry away waste and fluid). They can then spread to neighbouring lymph nodes or to distant areas of the body.
Colorectal cancer’s stage (the amount to which it has progressed) is determined by how deeply it has grown into the wall and whether it has gone outside the colon or rectum. For further information on staging,
Types of colon and rectal cancer
The majority of colorectal malignancies are adenocarcinomas. These malignancies begin in cells that produce mucus to lubricate the colon and rectum. When doctors discuss colorectal cancer, they virtually usually refer to this variety. Some subtypes of adenocarcinoma, such as signet ring and mucinous, may have a poorer prognosis (outlook) than others.
Other, far rarer forms of tumours can also begin in the colon and rectum. These are some examples:
1 Carcinoid tumours are cancerous tumours. These begin in the intestine from unique hormone-producing cells.
2 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, however, they are uncommon in the colon.
3 Gastrointestinal stromal tumours (GISTs) grow from Cajal interstitial cells located in the colon’s wall. Some are completely safe. (not cancer). These tumours can develop anywhere in the digestive tract, but they are most frequent in the colon.
4 Gastrointestinal stromal tumours (GISTs) grow from Canal interstitial cells located in the colon’s wall. Some are completely safe. (not cancer). These tumours can develop anywhere in the digestive tract, but they are most frequent in the colon.
