Colon cancer can be detected early before any symptoms develop with the proper screening techniques. At this point, it is easier to cure colorectal cancer.

To initially test for colon cancer, a doctor will perform a physical examination and press on the abdomen. The physical exam normally will not show any issues, although a doctor could feel a lump in the stomach. A rectal exam is often necessary to detect polyps or tumors in patients who have rectal cancer, although this will not yet diagnose colon cancer.

Colon Cancer Testing
In most cases, a fecal occult blood test, also called FOBT, will be used to test for blood in the stool, which could be a precursor to colon cancer. However, this test will often come back negative in many patients that have colon cancer. This is why an FOBT must be used in addition to a colonoscopy or sigmoidoscopy. Additionally, a positive FOBT does not always indicate that a patient has colon cancer.

The two most common imaging tests used to screen and diagnose colorectal cancer are:

• Colonoscopy: A colonoscopy is a test that uses a small camera attached to a tube. A colonoscopy will examine the entire length of the colon as the colonoscope is inserted into the rectum. In some cases, tissue samples may be taken for a biopsy using the scope. Polyps can also be removed using electrocautery snares; photographs may be taken for medical records.
• Sigmoidoscopy: A sigmoidoscopy is a test that uses a small camera attached to a tube. The tube will be inserted into the rectum and moved upward into the bowel. Air will be used to open the colon so that the doctor can see it better. Tissue samples can be taken for a biopsy using the scope. Visible polyps may be removed with electrocautery snares; photographs may be taken for medical records.

A colonoscopy differs from a sigmoidoscopy because it can reach throughout the entire length of the colon. A sigmoidoscopy can only examine the lower third of the colon.

Other blood tests may be used to detect colon cancer, like:

• CBC - A complete blood count to check for anemia.
• Liver function tests

Colon Cancer Staging
If colon cancer is detected, more testing is necessary to determine if and where the cancer has spread. This testing and diagnosis is known as staging. MRI or CT scans of the brain, chest, pelvis, and abdomen may be used to check for the spread of cancer. In some instances, PET scans may also be used.

AJCC (TNM) Staging System

A staging system is a standardized way in which the cancer care team describes the extent of the cancer. The most commonly used staging system for colorectal cancer is that of the American Joint Committee on Cancer (AJCC), sometimes also known as the TNM system. Older staging systems for colorectal cancer, such as the Dukes and Astler-Coller systems, are mentioned briefly below for comparison. The TNM system describes 3 key pieces of information:

• T describes how far the main (primary) tumor has grown into the wall of the intestine and whether it has grown into nearby areas.
• N describes the extent of spread to nearby (regional) lymph nodes. Lymph nodes are small bean-shaped collections of immune system cells that are important in fighting infections.
• M indicates whether the cancer has spread (metastasized) to other organs of the body. (Colorectal cancer can spread almost anywhere in the body, but the most common sites of spread are the liver and lungs.)

Numbers or letters appear after T, N, and M to provide more details about each of these factors. The numbers 0 through 4 indicate increasing severity. The letter X means "cannot be assessed because the information is not available."

T categories for colorectal cancer

T categories of colorectal cancer describe the extent of spread through the layers that form the wall of the colon and rectum. These layers, from the inner to the outer, include:

• The inner lining (mucosa)
• A thin muscle layer (muscularis mucosa)
• The fibrous tissue beneath this muscle layer (submucosa)
• A thick muscle layer (muscularis propria) that contracts to force the contents of the intestines along
• The thin, outermost layers of connective tissue (subserosa and serosa) that cover most of the colon but not the rectum

Tx: No description of the tumor's extent is possible because of incomplete information.

Tis: The cancer is in the earliest stage (in situ). It involves only the mucosa. It has not grown beyond the muscularis mucosa (inner muscle layer).

T1: The cancer has grown through the muscularis mucosa and extends into the submucosa.

T2: The cancer has grown through the submucosa and extends into the muscularis propria (thick outer muscle layer).

T3: The cancer has grown through the muscularis propria and into the outermost layers of the colon or rectum but not through them. It has not reached any nearby organs or tissues.

T4a: The cancer has grown through the serosa (also known as the visceral peritoneum), the outermost lining of the intestines.

T4b: The cancer has grown through the wall of the colon or rectum and is attached to or invades into nearby tissues or organs.

N categories for colorectal cancer

N categories indicate whether or not the cancer has spread to nearby lymph nodes and, if so, how many lymph nodes are involved. To get an accurate idea about lymph node involvement, most doctors recommend that at least 12 lymph nodes be removed during surgery and looked at under a microscope.

Nx: No description of lymph node involvement is possible because of incomplete information.

N0: No cancer in nearby lymph nodes.

N1: Cancer cells are found in or near 1 to 3 nearby lymph nodes

•   Cancer cells are found in 1 nearby lymph node.
•  Cancer cells are found in 2 to 3 nearby lymph nodes.
• Small deposits of cancer cells are found in areas of fat near lymph nodes, but not in the lymph nodes themselves.

N2: Cancer cells are found in 4 or more nearby lymph nodes

•  Cancer cells are found in 4 to 6 nearby lymph nodes.
•  Cancer cells are found in 7 or more nearby lymph nodes.

M categories for colorectal cancer

M categories indicate whether or not the cancer has spread (metastasized) to distant organs, such as the liver, lungs, or distant lymph nodes.

M0: No distant spread is seen.

M1a: The cancer has spread to 1 distant organ or set of distant lymph nodes.

M1b: The cancer has spread to more than 1 distant organ or set of distant lymph nodes, or it has spread to distant parts of the peritoneum (the lining of the abdominal cavity).

Stage grouping

Once a person's T, N, and M categories have been determined, usually after surgery, this information is combined in a process called stage grouping. The stage is expressed in Roman numerals from stage I (the least advanced) to stage IV (the most advanced). Some stages are subdivided with letters.

Stage 0

Tis, N0, M0: The cancer is in the earliest stage. It has not grown beyond the inner layer (mucosa) of the colon or rectum. This stage is also known as carcinoma in situ or intramucosal carcinoma.

Stage I

T1-T2, N0, M0: The cancer has grown through the muscularis mucosa into the submucosa (T1) or it may also have grown into the muscularis propria (T2). It has not spread to nearby lymph nodes or distant sites.

Stage IIA

T3, N0, M0: The cancer has grown into the outermost layers of the colon or rectum but has not gone through them (T3). It has not reached nearby organs. It has not yet spread to the nearby lymph nodes or distant sites.

Stage IIB

T4a, N0, M0: The cancer has grown through the wall of the colon or rectum but has not grown into other nearby tissues or organs (T4a). It has not yet spread to the nearby lymph nodes or distant sites.

Stage IIC

T4b, N0, M0: The cancer has grown through the wall of the colon or rectum and is attached to or has grown into other nearby tissues or organs (T4b). It has not yet spread to the nearby lymph nodes or distant sites.

Stage IIIA

One of the following applies.

T1-T2, N1, M0: The cancer has grown through the mucosa into the submucosa (T1) and it may also have grown into the muscularis propria (T2). It has spread to 1 to 3 nearby lymph nodes (N1a/N1b) or into areas of fat near the lymph nodes but not the nodes themselves (N1c). It has not spread to distant sites.

T1, N2a, M0: The cancer has grown through the mucosa into the submucosa (T1). It has spread to 4 to 6 nearby lymph nodes (N2a). It has not spread to distant sites.

Stage IIIB

One of the following applies.

T3-T4a, N1, M0: The cancer has grown into the outermost layers of the colon or rectum (T3) or through the visceral peritoneum (T4a) but has not reached nearby organs. It has spread to 1 to 3 nearby lymph nodes (N1a/N1b) or into areas of fat near the lymph nodes but not the nodes themselves (N1c). It has not spread to distant sites.

T2-T3, N2a, M0: The cancer has grown into the muscularis propria (T2) or into the outermost layers of the colon or rectum (T3). It has spread to 4 to 6 nearby lymph nodes (N2a). It has not spread to distant sites.

T1-T2, N2b, M0: The cancer has grown through the mucosa into the submucosa (T1) or it may also have grown into the muscularis propria (T2). It has spread to 7 or more nearby lymph nodes (N2b). It has not spread to distant sites.

Stage IIIC

One of the following applies.

T4a, N2a, M0: The cancer has grown through the wall of the colon or rectum (including the visceral peritoneum) but has not reached nearby organs (T4a). It has spread to 4 to 6 nearby lymph nodes (N2a). It has not spread to distant sites.

T3-T4a, N2b, M0: The cancer has grown into the outermost layers of the colon or rectum (T3) or through the visceral peritoneum (T4a) but has not reached nearby organs. It has spread to 7 or more nearby lymph nodes (N2b). It has not spread to distant sites.

T4b, N1-N2, M0: The cancer has grown through the wall of the colon or rectum and is attached to or has grown into other nearby tissues or organs (T4b). It has spread to at least one nearby lymph node or into areas of fat near the lymph nodes (N1 or N2). It has not spread to distant sites.

Stage IVA

Any T, Any N, M1a: The cancer may or may not have grown through the wall of the colon or rectum, and it may or may not have spread to nearby lymph nodes. It has spread to 1 distant organ (such as the liver or lung) or set of lymph nodes (M1a).

Stage IVB

Any T, Any N, M1b: The cancer may or may not have grown through the wall of the colon or rectum, and it may or may not have spread to nearby lymph nodes. It has spread to more than 1 distant organ (such as the liver or lung) or set of lymph nodes, or it has spread to distant parts of the peritoneum (the lining of the abdominal cavity) (M1b).

 

Regular colon cancer screenings and checkups are the best ways to prevent colon cancer in women. It is important to test regularly to detect and remove colon polyps to prevent the development of cancer. In most cases, regular screening will detect colon cancer early on to increase the likelihood of a cure.

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Ovarian Cancer	Introduction: Causes and Risk Factors	Symptoms	Diagnosis and Staging	Treatment
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Source: "Colon cancer - PubMed Health." National Center for Biotechnology Information. N.p., n.d. Web. 13 Oct. 2011.