Colon cancer diagnosis and staging

In order to properly diagnose colon cancer and the type you might have—and to help determine the best treatment plan—your team of providers might use a number of different exams and procedures.

Medical history and physical exam. Your doctor will take your medical history, and will ask about any symptoms, including when they started and how long you’ve had them. As part of a physical exam, your doctor will feel your abdomen for masses or enlarged organs, and also examine the rest of your body. You may also have a digital rectal exam (DRE). During this test, the doctor inserts a lubricated, gloved finger into your rectum to feel for any abnormal areas.

Tests to look for blood in your stool. Your doctor may recommend a test to check your stool for blood that isn’t visible to the naked eye, called occult blood. You would do this at home, either a fecal occult blood test (FOBT) or fecal immunochemical test (FIT).

Blood tests. Your doctor might also order certain blood tests to be used to help monitor your disease if you’ve been diagnosed with cancer.

Complete blood count (CBC). This test measures the different types of cells in your blood, and it can show if you have anemia.

Liver enzymes. You may also have a blood test to check your liver function, because colorectal cancer can spread to the liver.

Tumor markers. Blood tests for these tumor markers can sometimes suggest someone might have colorectal cancer, but they can’t be used alone to screen for or diagnose cancer.

Diagnostic colonoscopy. Your doctor looks at the entire length of your colon and rectum with a colonoscope, a thin, flexible, lighted tube with a small video camera on the end. Special instruments can be passed through the colonoscope to biopsy or remove any suspicious-looking areas such as polyps.

Proctoscope. May be done if rectal cancer is suspected. Your doctor looks inside the rectum with a proctoscope, a thin, rigid, lighted tube with a small video camera on the end. The tumor can be seen, measured, and its exact location can be determined.

Biopsy. The definitive step in a proper diagnosis. Your doctor removes a small piece of tissue with a special instrument passed through a scope. A pathologist examines the biopsy samples under a microscope, and if cancer is found, other lab tests may also be done on the biopsy specimens to help better classify the cancer.

Imaging tests

Imaging tests use sound waves, x-rays, magnetic fields, or radioactive substances to create pictures of the inside of your body. Possible tests include:

  • Computed tomography (CT or CAT) scan. Helps us see if colon cancer has spread into your liver or other organs.
  • Abdominal ultrasound. Can be used to look for tumors in your liver, gallbladder, pancreas, or elsewhere in your abdomen, but it can’t look for tumors of the colon.
  • Endorectal ultrasound. Used to see how far through the rectal wall a cancer has grown and whether it has reached nearby organs or tissues such as lymph nodes.
  • Intraoperative ultrasound. Done during surgery, allowing the surgeon to biopsy the tumor while the patient is asleep.
  • Magnetic resonance imaging (MRI) scan. Can be used to look at abnormal areas in the liver or the brain and spinal cord that could be cancer spread.
  • Endorectal MRI. MRI scans can be used in patients with rectal cancers to see if the tumor has spread into nearby structures.
  • Positron emission tomography (PET) scan. If you have already been diagnosed with cancer, your doctor may use this test to see if the cancer has spread to lymph nodes or other parts of the body. Some machines can do both a PET and CT scan at the same time.
  • Angiography. An x-ray test for looking at blood vessels.
  • Chest x-ray. May be done after colorectal cancer has been diagnosed to see if cancer has spread to the lungs.

UCHealth follows the American Joint Committee on Cancer (AJCC) TNM system, the staging system most often used for colorectal cancer. It is based on three key pieces of information:

  1. The extent (size) of the tumor (T).
  2. The spread to nearby lymph nodes (N).
  3. The spread (metastasis) to distant sites (M).

The system described below is the most recent AJCC system, effective January 2018.

Cancer staging can be complex, so ask your doctor to explain it to you in a way you understand.

AJCC Stage Stage grouping Stage description*
0 Tis
N0
M0
The cancer is in its earliest stage. This stage is also known as carcinoma in situ or intramucosal carcinoma (Tis). It has not grown beyond the inner layer (mucosa) of the colon or rectum.
I T1 or T2
N0
M0
The cancer has grown through the muscularis mucosa into the submucosa (T1), and it may also have grown into the muscularis propria (T2). It has not spread to nearby lymph nodes (N0) or to distant sites (M0).
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 spread to nearby lymph nodes (N0) or to distant sites (M0).
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 nearby lymph nodes (N0) or to distant sites (M0).
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 nearby lymph nodes (N0) or to distant sites (M0).
IIIA
T1 or T2
N1/N1c
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 (N1) or into areas of fat near the lymph nodes but not the nodes themselves (N1c). It has not spread to distant sites (M0).
–OR–
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 (M0).
IIIB

T3 or T4a, N1/N1c
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 or N1b) or into areas of fat near the lymph nodes but not the nodes themselves (N1c). It has not spread to distant sites (M0).
–OR–
T2 or 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 (M0).
–OR–
T1 or T2 N2b
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 7 or more nearby lymph nodes (N2b). It has not spread to distant sites (M0).
IIIC
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 (M0).
–OR–
T3 or 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 (M0).
–OR–
T4b
N1 or 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 (M0).
IVA Any T
Any N
M1a
The cancer may or may not have grown through the wall of the colon or rectum (Any T). It might or might not have spread to nearby lymph nodes. (Any N). It has spread to 1 distant organ (such as the liver or lung) or distant set of lymph nodes, but not to distant parts of the peritoneum (the lining of the abdominal cavity) (M1a).
IVB Any T
Any N
M1b
The cancer might or might not have grown through the wall of the colon or rectum (Any T). It might or might not have spread to nearby lymph nodes (Any N). It has spread to more than 1 distant organ (such as the liver or lung) or distant set of lymph nodes, but not to distant parts of the peritoneum (the lining of the abdominal cavity) (M1b).
IVC Any T
Any N
M1c
The cancer might or might not have grown through the wall of the colon or rectum (Any T). It might or might not have spread to nearby lymph nodes (Any N). It has spread to distant parts of the peritoneum (the lining of the abdominal cavity) and may or may not have spread to distant organs or lymph nodes (M1c).

Source: American Cancer Society