Cancer staging is a method in which doctors can determine how much the cancer has spread throughout the body, according to the American Cancer Society. It is based upon physical exams, imaging tests and biopsies. The clinical stage is useful in determining the best treatment for the cancer. There are two different types of staging: TNM (tumor, node, metastasis) and Roman numeral staging. TNM staging focuses on the tumor description, lymph node involvement and the spread of cancer to other organs or metastasis. Roman numeral staging groups TNM into one to four different stages.
Tumor
The first part of TNM staging is the description of the tumor. The most important factors are the size of the tumor and how much it has spread into the tissues around it. T0 means that the primary tumor cannot be found, or is present, but is very small and not invaded the surrounding tissues. T1 to T4 represents a scale measuring the size of the tumor and whether it has grown into nearby tissues. The higher the number the larger the tumor and the more it has invaded neighboring cells.
Lymph Node Involvement
The N part of TNM staging is limited to N0, N1, N2 and N3, according to CancerHelp UK. The N stands for the number of lymph nodes affected by the cancer and whether they are near the primary tumor or far from the tumor. N0 means that there is no lymph node involvement, N1 means one nearby lymph node is affected, N2 indicates that multiple nearby lymph nodes have been invaded by the cancer, and N3 is when the cancer has affected one or more lymph nodes further away from the primary cancer.
Metastasis
Metastasis refers to the spread of the cancer to other organs. For staging purposes the M in TNM staging is either M0 or M1, according to CancerGuide.org. M0 means that the cancer has yet to spread to other organs, and M1 means that the cancer has spread to other parts of the body.
Roman Numeral Staging
Once the TNM staging of the cancer has been established the cancer is placed into groups. These groups, according to the American Cancer Society, range from 0 to IV. The lower the Roman numeral the lower the score on the TNM staging.
A tumor that is T1, N0, M0 means that the primary tumor is less than 2 cm across (T1), does not involve any lymph nodes (N0), and has not spread to any other organs (M0). This TNM score correlates to a stage I cancer.
Stage 0 cancer corresponds to a small cancer that has not spread at all to any nearby tissues and is only found in one specific region. Stage I cancer means that the cancer is small, but may have already slightly affected nearby cells, Stage II cancer means the cancer is slightly larger, and may have invaded more tissues that a stage I cancer. Stage II cancers may also have infiltrated a nearby lymph node. Stage III cancers have grown larger than 2 cm and may have infiltrated many lymph nodes. Stage IV cancer is any cancer that has already spread to other organs.
