Colorectal Cancer

Colorectal Cancer

Colorectal cancer is one of the most common types of cancers. It can be found anywhere in the large bowel, also called the colon, and the rectum. The large bowel is the last part of the digestive system and helps break down food, absorb water and remove waste.

There are many causes for bowel cancer but often the cause is not known. It can be caused by genetic factors, lifestyle factors and environmental factors. Having certain risk factors can increase the likelihood of developing colorectal cancer. These include: Age over 40 (although colorectal cancer can occur at any age it is more common over the age of 40), overweight or obesity, family history, inherited conditions that increase the risk of colon cancer (such as Lynch Syndrome or Familial Adenomatous Polyposis (FAP), having an inflammatory disease (which includes Crohn’s disease and ulcerative colitis) and having a history of small growths in the bowel called polyps.

Symptoms of colorectal cancer include altered bowel habit, bloating, blood in stools, rectal bleeding, fatigue, reduced appetite, nausea and vomiting, and unintentional weight loss.

Examples of locations where colorectal cancers can develop
Stool sample with blood
A small number of bowel cancers are thought to be due to changes in genes (variants), which are segments of DNA that are inherited and pass down through a family. Affected individuals (red) in example family tree
Staging a bowel cancer involves describing its size, including how deeply it has grown into the wall of the colon, where it is and whether it has spread to other parts of the body. This helps decide on what is the best treatment
Stage 0
Limited to mucosa
Stage 1
Extending into submucosa
Stage 2
Muscle wall breached
Stage 3
Lymph nodes involved
Stage 4
Spread to other organs
Lymph node
Layers of the bowel wall
Muscle layers
The vast majority of colorectal cancers are adenocarcinomas—these start in glands that line the insides of the organs.
Under a microscope the abnormal cells (seen on the left) vary in their size, shape and nuclei compared to normal cells.

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