After the diagnosis of cancer, the stage of the disease is determined. Stage refers to how advanced a cancer is, how aggressive it is and what is the prognosis in terms of spreading.

The TNM system is the most commonly used staging system, including colorectal cancer.

T

(T) describes tumor size and maybe 4 stages in colorectal cancer:

• T1: the tumor is only in the superficial layer of the colon;
• T2: the tumor has developed in the colon wall musculature;
• T3: the tumor has developed into the inner layer of the colon wall;
• T4: The tumor has developed through the internal wall of the colon to other organs, regions or structures.

N

(N) describes the spread of cancer to lymph nodes and has 3 stages:

• NO: Cancer cells did not spread to the lymph nodes;
• N1: cancer cells spread to 1-3 nearby lymph nodes;
• N2: The cancer cells spread to 4 or more lymph nodes

M

(M) describes the spread of cancer to other regions of the body and has two stages:

• M0: cancer has not spread to other organs;
• M1: cancer has spread to other regions of the body.