The colon cancer staging is done based on the TNM system of staging.
Read more on what is colon cancer here {insert primary article hyperlink here}.
The TNM system of staging has the following factors:
Tumor (T): This factor indicates how far the cancer has grown into the wall of the colon. These layers include, the mucosa which is the inner lining, the sub mucosa which is the fibrous tissue below the muscle, the muscularis propria which is a thick muscle layer and the serosa and suberosa which are a thin layer of connective tissue.
Lymph node s (N): This factor indicates if the cancer has spread to the lymph nodes.
Metastasis (M): This factor refers to whether the cancer has spread to other parts of the body.
Stage 3 can further be classified into stage 3A, 3B or 3C.
In stage 3 colon cancer, the diagnosis for the substages is done according to the following TNM categories:
Stage 3A:
T1:
The cancer has grown through the mucosa of the colon wall into the submucosa.
N2a:
The cancer has spread to 4 to 6 nearby lymph nodes
M0:
The cancer has not spread to distant organs or sites.
Or
T1 or T2:
The cancer has grown through the mucosa into the submucosa(T1) or through the muscularis propria(T2).
N1 or N1c:
The cancer has spread to 1 to 3 lymph nodes (N1a or N1b) or the cancer has spread like deposits in subserosa, tissues adjacent to the colon bot not to the lymph nodes (N1c).
M0:
The cancer has not spread to distant organs or sites.
Stage 3B
T1 or T2:
The cancer has grown through the mucosa and into the submucosa of the colon (T1) it may have also grown into the muscularis propria (T2).
N2b:
The cancer has spread to 7 or more of the nearby lymph nodes.
M0:
The cancer has not spread to distant organs or sites.
Or
T2 -T3:
The cancer has grown through the submucosa into the muscularis propria(T2) or sub serosa(T3)
N2a:
The cancer has spread to 4 to 6 nearby lymph nodes
M0:
The cancer has not spread to distant organs or sites.
Or
T3 -T4a
Involvement of subserosa(T3) Or serosa without adherent to surrounding tissues(T4a)
N1/N1C
The cancer has spread to 1 to 3 lymph nodes (N1a or N1b) or the cancer has spread like deposits in subserosa, tissues adjacent to the colon bot not to the lymph nodes (N1c).
M0
Cancer has not spread to the distant organs
Stage 3C
T3 or T4a:
The cancer has grown through the outermost layers of the colon (T3) or through the visceral peritoneum.
N2b:
The cancer has spread to 7 of more of the nearby lymph nodes.
M0:
The cancer has not spread to distant organs or sites.
Or
T4b:
The cancer has grown through the wall of the colon or rectum and is attached to or has grown into nearby tissues.
N1or N2
The cancer has spread to at least 1 nearby lymph node or it has also spread into the fat areas near the lymph nodes (N1 or N2).
M0:
It has not spread to distant sites.
Or
T4a
Cancer has spread to the serosa but not adherent to the surrounding tissues
N2a
The cancer has spread to 4 to 6 nearby lymph nodes
MO
It has not spread to distant sites.
