Colon cancer happens when cells in the colon start growing abnormally and turn cancerous. This is curable if it is treated at an early stage. This article talks about how colon cancer stages are determined. This will help in understanding the stages and treatment for colon cancer.

Importance of staging
Cancer is a progressive disease. It can start as a small lump of cells and can gradually or suddenly start growing. To know how to treat cancer, it is important to understand the stages and treatment for colon cancer for a particular stage.

TNM staging
Cancer stages are decided using the TNM system. This is used by the doctor to decide at what stage the cancer is in.

• T stands for the primary tumor. It refers to the size of the tumor and whether it is restricted to the wall of the colon where it started or has spread to other areas.
• N for lymph nodes. It refers to whether the lymph nodes that nearby the colon have turned cancerous due to the spreading of the cancer.
• M stands for metastases. It refers to whether the cancer has spread from the colon and reaches other body parts like the liver, or lungs.

Based on this classification, colon cancer is classified from Stage 0 to Stage 4.

Stage 0
Here, cancer cells are restricted to the innermost layers or the lining of the colon or the rectum. This is known as in situ cancer. This is the earliest stage and detection at this stage is very difficult.

Stage 1
From the inner layer of the colon, the cancer cells start spreading and first reach the submucosa. It is still restricted to within the colon. This stage is known as Stage 1.

Stage 2
In this stage, cancer cells have spread beyond the mucosa and submucosa. It is further classified as:

• 2A: Where cancer has reached the outer layers of the colon.
• 2B: Where cancer has crossed the outer layer and moved to the peritoneum membrane.
• 2C: Where cancer has crossed the colon and started spreading to nearby organs but has not yet reached the lymph nodes.

Stage 3
In this stage, the cancer cells would have crossed the colon and reached the lymph nodes. It is classified as:

• 3A: Where the nearby lymph nodes have been affected by the cancer cells.
• 3B: Where cancer cells have spread to one or more than one lymph node and have entered nearby organs also.
• 3C: The cancer is still localized to the colon and nearby organs but has spread to four or more of the lymph nodes in the area.

Stage 4
This is the most serious stage, classified as:

• 4A: Where the cancer has spread to the liver or lungs.
• 4B: The most advanced stage of cancer having spread to at least two distant sites.

Before understanding more about the stages and treatment for colon cancer, it is important to understand about staging. The information in the article would have helped you understand the stages of colon cancer and what it means for treatment.