Cancer is characterized by the unchecked multiplication of cells in the body, leading to a tumor When such abnormal growth occurs in the colon or rectum, it is called colorectal cancer or colon cancer. The colon and rectum combined are called the large intestine and are the final part of the gastrointestinal (GI) system. The function of the GI system is to process food for energy and to get rid of the solid waste from the body.
How does colon cancer develop?
Colon cancer usually begins as a noncancerous growth called a polyp, which develops on the inner lining of the large intestine and slowly grows over a period of 10 to 20 years. An adenomatous polyp also called an adenoma, is the most common type of colon cancer.
Once cancer forms in the large intestine, it proceeds to grow into the wall of the colon or rectum. Later, cancer can also infiltrate the blood or lymph vessels which are the thin channels that transport cellular waste and fluid. Sometimes cancer cells get carried in blood vessels also, which further reaches the other organs and tissues like the lungs, liver, or peritoneum. The spread of cancer cells to other distant body parts from where the tumor originated is called metastasis.
What are the stages of colon cancer?
The extent to which cancer has spread at the time of diagnosis is described as its stage. Staging helps to determine the treatment choices and assessing prognosis. The two of the most common cancer staging systems are the TNM system, which is used in a typical clinical setting, and the Surveillance, Epidemiology, and End Results (SEER) summary staging system that is used for a more descriptive and statistical analysis of tumor. The following describes the stages of colon cancer based on the SEER staging system.
- In situ: This refers to the stage wherein cancer has not yet begun to invade the wall of the colon or rectum.
- Local: When cancer has grown into the wall of the colon or rectum, but still has not extended through the wall, it is called the local stage.
- Regional: When cancer spreads through the wall of the large intestine and has invaded nearby tissue, or to nearby lymph nodes, it means it is at the regional stage.
- Distant: When cancer spreads to the other parts of the body like the liver or lung, it will come under distant cancer.
What are the symptoms of colon cancer?
Early colon cancer often shows no symptoms, which is why screening is so important. Once a tumor starts growing it may bleed or obstruct the intestine. Some cases even lead to blood loss causing anemia (low number of red blood cells) with symptoms like weakness, fatigue, and sometimes shortness of breath along with other warning signs as mentioned.
- Bleeding rectum
- Discomfort or cramps in the lower abdomen
- Blood in the stool or toilet after having a bowel movement
- Black or dark stools
- Constipation or diarrhea for more than a few days
- A constant urge to have a bowel movement even when the bowel is empty.
- Unintentional weight loss
- Decreased appetite
