Colon Cancer Staging

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Applied Anatomy of Human Colon

This pouch-like structure, present at the beginning of the colon is called as caecum. caecum This part, present on the right side of the abdomen, extending upwards from the caecum is called an ascending colon. ascending colon The longest part of the colon, that extends from the right to the left side of the abdomen, is called as transverse colon. transverse colon And this part, which extends downwards from transverse colon, on the left side of the abdomen, is called as descending colon. descending colon And this last part, which connects colon to the rectum and anal canal is called as sigmoid colon. sigmoid colon These are the loops of the small intestine that occupy the central part of the abdomen. This is the cross-section from the wall of the colon, with the upper part being inside and lower part being outside of the wall. cross section from the wall of the colon The innermost layer is epithelium, followed by this layer called as lamina propria. Outer to which lies muscularis mucosa. Then comes the submucosa. Outer to which lies the muscularis propria which is followed by a layer of pericolorectal tissue. On the outermost aspect, lies this layer which is called as serosa.

TNM Staging of Colon Cancer

T Staging

TisPre-cancerous or cancer cells present only in the superficial layer (epithelium) of colorectal mucosa

T1 – Cancer extends to the lamina propria

T2 – Cancer extends to the muscular layer (muscularis propria)

T3 – Cancer extends through the muscularis propria into the pericolorectal tissues

T4a – Cancer has invaded up to the outermost serosa layer (or visceral peritoneum)

T4b – Cancer has invaded into the adjacent structures/organs like small intestine, kidneys, pancreas, or stomach.

colon cancer T staging-T1 T2 T3 T4

N Staging

Now we will discuss the N staging or the nodal staging for colon cancer. In this figure, you can see the draining lymph nodes for the colon. colon cancer N staging It can be called as N0, N1 or N2, depending upon the number of lymph nodes involved.

N0 – Cancer has not spread to regional lymph nodes

N1 – Cancer has spread to 1 to 3 nearby lymph nodes

N2a – Cancer has spread to 4 to 6 nearby lymph nodes.

N2b – Cancer has spread to >/=7 nearby lymph nodes.

M Staging

Lastly, we will discuss the M-staging or the metastatic staging of the colon cancer.  Liver is the most common site for the distant spread of the tumor from colon.

Due to the direction of vascular drainage, after liver, lungs are the second most common organs involved by metastasis.

This figure shows the spread of colon cancer to both the lungs, in form of multiple nodular deposits. And sometimes, both lungs and liver maybe involved in the metastatic spread of the disease, as we can see in this figure. metastasis to both lungs The tumor may also spread to the peritoneum, in form of peritoneal deposits. spread to the peritoneum It may rarely spread to one or both the ovaries. Very rarely, the tumor may also spread to the brain or bones.

M1a – Cancer has spread to one distant organ without peritoneal spread.

M1b – Cancer that has spread to >/=2 distant organs without peritoneal spread.

M1c – Cancer that has spread to peritoneum with or without other sites.

colon cancer N and M staging

4 Stages of Colon Cancer

Based on the TNM classification described above, colon cancer may be divided into 4 stages as descibed below.

Stage TNM
0 Tis N0 M0
I T1-2 N0 M0
IIA T3 N0 M0
IIB T4a N0 M0
IIC T4b N0 M0
IIIA T1-2 N1/1c M0
  T1 N2a M0
IIIB T3-4a N1/1c M0
  T2-3 N2a M0
  T1-2 N2b M0
IIIC T4a N2a M0
  T3-4a N2b M0
  T4b N1-2 M0
IVA Any T Any N M1a
IVB Any T Any N M1b
IVC Any T Any N M1c

Stage 1 Colon Cancer

Stage 1 colon cancer includes cases with T1 and T2 disease, that is, disease extending upto muscularis propria. 

As you can see in the figure below, colon cancer extends up to the submucosa. If it is only limited upto the submucosa, it is called as T1 disease.
T1b-infiltration into submucosa
In the following figure, it extends upto the muscularis propria. Such cases when colon cancer extends deeper to infiltrate into muscle layer, it is called T2.
 
T2, extends up to the muscular propriaT1 and T2 colon cancer comes under stage 1 disease.

Stage 2 Colon Cancer

It includes cases of T3 and T4 disease.
 

In T3, cancer extends through the muscularis propria into the pericolorectal tissues.

stage 2 colon cancer,  t3 disease involving pericolorectal tissue

In T4a, cancer has invaded up to the outermost serosa layer of colonic wall.

stage 2 colon cancer, t4a disease involving serrosa or adventitia

In T4a, colon cancer has invaded into the adjacent structures/organs like small intestine, kidneys, pancreas, or stomach.

A tumor present in almost any part of the colon may infiltrate into the small intestine.

tumor from any part of colon can involve small intestine Tumor in the ascending colon may infiltrate into the right kidney. ascending colon tumor infiltrating right kidney And that in the descending colon may infiltrate into the left kidney. descending colon tumor infiltrating left kidney A transverse colon tumor may extend to involve pancreas. transverse colon tumor infiltrating pancreas And may even extend to involve the stomach. transverse colon tumor infiltrating stomach

Stage 3 Colon Cancer

All node positive cases come under stage 3 disease. It may be N0, N1 or N2 depending upon the number of lymph nodes involved. It has been discussed above in N staging.

Stage 4 Colon Cancer

It is also called as metastatic colon cancer. When the disease spread to non-regional lymph nodes or distant sites, it is called as stage 4. It has been discussed in detail above in M staging.

Survival/Life Expectancy of Colon Cancer based on Staging

Localised 

  • Cancer is limited to the bladder.
  • 5 year survival 90%.

Regional

  • Cancer has spread to nearby structures or lymph nodes
  • 5 year survival 71%.

Distant

  • Cancer has spread to distant body parts like lungs, liver or bones.
  • 5 year survival 14%.

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