Colon cancer is sometimes called colorectal cancer, which is a term that combines colon cancer and rectal cancer, which begins in the rectum. Colon cancer and rectal cancer are often grouped together. Cancer starts when cells in the body start to grow out of control.

Understanding the normal structure of the colon and rectum will eventually help us understand colon and rectum cancer. The colon and rectum form the large intestine, which is part of the digestive system, also called as gastrointestinal (GI) system. The parts of the colon are named according to which way the food is traveling.

Ascending colon - The cecum is the pouch where undigested food comes in from the small intestine. It continues upward on the right side of the abdomen.

Transverse colon - The food then moves from the right to the left side of the body. 

Descending colon - Because the food then travels down on the left side.

Sigmoid colon - The sigmoid colon joins the rectum, which then connects to the anus.

Polyps:

The majority of colorectal cancers begin as tumours on the rectum or colon's inner lining. These growths are called polyps. There are different types of polyps:

Adenomatous polyps (adenomas): Adenomas are called a pre-cancerous condition. The three types of adenomas are tubular, villous, and tubulovillous.

Hyperplastic polyps and inflammatory polyps: These types of polyps are common, and they are not pre-cancerous. In this case, some people with large hyperplastic polyps might need colorectal cancer screening with a colonoscopy.

Sessile serrated polyps (SSP) and traditional serrated adenomas (TSA): Because these polyps have a high risk of colorectal cancer, they are often treated like adenomas.

How does cancer develop or spread?

Your colon wall is made up of many layers, including mucous membranes, tissue, and muscle. Colorectal cancer starts in the innermost layer, which is the mucosa, and can grow outward through some or all of the other layers. It consists of cells that make and release mucus and other fluids. If these cells mutate or change, they may create a colon polyp.

Over time, colon polyps may become cancerous. (It usually takes about 10 years for cancer to form in a colon polyp.) Left undetected and/or untreated, colon cancer may also spread to other parts of your body via lymph nodes or blood vessels.

Risk factors for colon cancer:

Smoking- Products like tobacco and cigarettes increase your risk of developing colon cancer.

Excessive alcohol consumption- Limiting your alcohol consumption can reduce the chances of colon cancer.

Obesity- Eating high-calorie foods may increase your weight, which can be sign of colon cancer.

Excesive red meat and processed meat consumption- Doctors suggest reducing the consumption of meat to twice a week.

Not exercising- Exercise lowers the risk of developing any disease; it may also lower the risk of colon cancer. 

Types of cancer in the colon and rectum:

• Carcinoid tumors
• Gastrointestinal stromal tumors (GISTs)
• Lymphomas
• Sarcomas

Symptoms:

You may not know whether you have colon cancer because some symptoms are similar to those of less serious conditions. Here are some common symptoms of colon cancer:

• Blood in your stool
• Bloated stomach
• Abdominal Pain
• Vomitting
• Unexplained weightloss

(Disclaimer: The content on this site is for informational purposes only, and should not be taken as professional medical advice.  Always seek the guidance of your doctor or other health professionals for any questions you may have regarding your health or a medical condition.)