Colorectal Cancer

Colorectal Cancer overview and Definition

Colorectalal cancer is the malignant transformation of the colon and rectum of the cancer.


 the peak incidence appears in the 5th decade of the life and it is the third most common cancer in men.

Structure of Colorectal Cancer

The colon is the part of the large intestine. It includes ascending colon, descending colon, transverse colon, caecum.

Ascending colon:

It is the starting point of the large intestine. Undigested foods are absorbed here.

The main function of the ascending colon is to reabsorb water and nutrients from the waste materials

Transverse colon:

It transfers the food from one side to the opposite side.

Descending colon:

It is present in the left side of the pelvic region just beneath the diaphragm.

Sigmoid colon:

The sigmoid colon is ‘S’ shaped organ

The sigmoid colon is the last part of the large intestine and it is present between the rectum and colon.

The ileocaecal valve paves the connection between the small intestine and the colon. And it also demarcates the caecum from the colon.


The rectum is the lower part of the large intestine that connects to the sigmoid colon. It is about 15 cm (6 in) long. It receives waste from the colon and stores it until it passes out of the body through the anus.



The genetic and other triggering factors leads to the activation of the oncogenes and inactivation of the tumour suppressor genes.

Inactivation of the DNA repair mechanisms

Clinical signs & symptoms

  • rectal bleeding or blood in the stool,
  • dark-colored stool,
  • change in bowel habits,
  • change in stool consistency,
  • constipation,
  • diarrhea,
  • narrow stools
  • weight loss
  • iron deficiency anaemia

Differential Diagnosis


The patient is sedated and physician looks for an abnormality in the intestine with a computer aided device.


It is the removal of a small amppount of tissue for examination under the microscope. A biopsy is the confirmatory test for colorectal cancer or colonal cancer.

Biomarketing testing of the tumour:

The colorectal cancer should be tested for problems in mismatch repair proteins called mismatch repair defect.

Blood test:

Patient with the colorectal cancer may tends to bleed through rectum. This results in the aneamia in patients. Complete blood count might reveal whether the bleeding is occurring or not.

Other levels of protein such as the carcinoembryonic antigen which detects if the cancer has spread to other regions or not.

Fecal immunochemical test:(FIT0

This test reveals if the blood is present in the stool or not

Guaiac based feacl occult blood test(gFOBT):

It is similar to the FIT but it reveals the occult blood in stool.

Fecal DNA test:

It tests the genetic mutations and presence of cancer cells in the stool.

Computed tomography:

A CT scan takes three dimensional pictures of the abnormal tissues from different angles.

Magnetic Resonance Imaging:

A MRI scan uses the combination of the magnetic and radiowave frequency to view the abnormal tissues.

An dye is injected in the vein or the patient is asked to swallow the dye and the results are observed.


A sound waves to create the picture of the internal organs to find out if the cancer is spread or not.

Chest x ray:

The chest x ray might reveals whether the cancer has spread to the lungs or not

Positron emission tomography (PET) or PET-CT scan.:

A PET scan is a way to create pictures of organs and tissues inside the body. A small amount of a radioactive sugar substance is injected into the patient’s body. This sugar substance is taken up by cells that use the most energy. Because cancer tends to use energy actively, it absorbs more of the radioactive substance. However, the amount of radiation in the substance is too low to be harmful. A scanner then detects this substance to produce images of the inside of the body.

  • Stages:
  • Stage 0:
  • The cancer is not spread but has potential development of the cancer in the future which is termed as carcinoma insitu.
  • Stage 1:
  • The cancer cells are consider to the localized area. This is also called the early stage cancer
  • Stage 2 and Stage 3:
  • It indicates that the cancer cell has spread to the nearby lymphnodes or tissues.
  • Type 4 :
  • It indicates that the cancer has spread to other parts of the body and also it easily gets metastasis. This is also called an advanced type of cancer.



 Another common staging tool is the TNM system, which stands for Tumor, Node, Metastasis. When a patient’s cancer is staged with TNM, a number will follow each letter. This number signifies the extent of the disease in each category. According to the National Cancer Institute and MD Anderson experts, the standard TNM system uses the following rules:

Primary tumor (T)

  • TX: Main tumor cannot be measured.
  • T0: Main tumor cannot be found.
  • T(is), or T in situ: The tumor is still within the confines of the normal glands and cannot metastasize.
  • T1, T2, T3, T4: Refers to the size and/or extent of the main tumor. The higher the number after the T, the larger the tumor or the more it has grown into nearby tissues. T's may be further divided to provide more detail, such as T3a and T3b.

Regional lymph nodes (N)

Lymphatic fluid transports immune system cells throughout the body. Lymph nodes are small bean-shaped structures that help move this fluid. Cancer often first spreads to and through nearby lymph nodes.

  • NX: Cancer in nearby lymph nodes cannot be measured.
  • N0: There is no cancer in nearby lymph nodes.
  • N1, N2, N3: Refers to the number and location of lymph nodes that contain cancer. The higher the number after the N, the more lymph nodes that contain cancer.

Distant metastasis (M)

Metastasis is the spread of cancer to other parts of the body.

  • MX: Metastasis cannot be measured.
  • M0: Cancer has not spread to other parts of the body.
  • M1: Cancer has spread to other parts of the body.



The 5 year survival rate of the colorectalal cancer is 80%.


Intake of fiber foods

Avoid smoking

Avoid alcohol consumption

Increases the physical activity- aids in digestion process

Drink lots of water

Eat well cooked foods