After a colorectal cancer diagnosis, you likely experience a range of emotions. Allow yourself to be present with all your emotions, and communicate with your support network (family, friends, or mental health professional) to help you manage this unexpected event. You may have a desire to begin treatment immediately, but know that before beginning treatment you must go through the steps of cancer staging to learn more about your cancer and how to treat it.

It is important that you take the time to learn about your colon cancer or rectal cancer diagnosis because your diagnosis determines the treatment you will receive. Once your doctor tells you that you have colon or rectal cancer, your healthcare team will work together to determine what stage of diagnosis you have. Learn as much as you can about your diagnosis before making cancer treatment decisions. If there is any uncertainty about your diagnosis or treatment choices, you’ll benefit from a second opinion.

Call our Patient Resources Line for help with your colorectal cancer diagnosis or to get resources for colorectal cancer patients. Also, if you’re stage III or stage IV, download Your Guide in the Fight.


Step 1

First, you will have blood tests (to look for certain enzymes), diagnostic scans (to show where the cancer is located), and a physical exam:

  • A computed tomography (CT) scan is an imaging method that uses x-rays to create pictures of cross-sections of the body.
  • A positron emission tomography (PET) scan is an imaging test that uses a radioactive substance called a tracer that creates 3-D images to look for disease in the body.

Need more information about your radiology exam? Visit

Step 2

Surgery may be the next step. Doctors may want to conduct a biopsyto remove cells from the tumor and have a pathologist examine them to determine whether they appear normal (called cell differentiation).

  • Your tumor should be tested for biomarkers. This can help guide treatment recommendations and decisions.

Step 3

Your cancer is finally classified according to the TNM system (tumor, node, metastasis) developed by the American Joint Committee on Cancer (AJCC).

  • >Tumor: How far the tumor extends from the inner lining of the colon or rectum through the layers of its walls
  • Nodes: Whether cancer cells are found in the lymph nodes by the colon
  • Metastasis: Whether cancer has spread beyond the colon and its adjacent tissues to organs like the lungs or liver

Step 4

After doctors classify a tumor with the TNM system, an overall stage is assigned, ranging from stage 0 (no cancer found) to stage IV (cancer spread to organs beyond the colon or rectum).

Stage TNM Classification
Stage 0 Tis, N0, M0
Stage I T1-T2, N0, M0
Stage IIA T3, N0, M0
Stage IIB T4a, N0, M0
Stage IIC T4b, N0, M0
Stage IIIA T1-T2, N1, M0T1, N2a, M0
Stage IIIB T3-T4a, N1, M0T2-T3, N2a, M0T1-T2, N2b, M0
Stage IIIC T4a, N2a, M0T3-T4a, N2b, M0T4b, N1-N2, M0
Stage IVA Any T, Any N, M1a
Stage IVB Any T, Any N, M1b

Colorectal Cancer Diagnosis & Biomarkers

You’ll want to have your tumor tested for Biomarkers at the time of rectal or colon cancer diagnosis. Biomarkers play a key role in developing individualized treatment plans. Getting your tumor tested for biomarkers could help you choose a treatment plan that best matches your tumor type so you may you may experience fewer side effects and improved health.

Here is a list of known biomarkers that impact colorectal cancer patients. For more information about their implications, visit the Biomarked website.

  • KRAS and NRAS
  • BRAF
  • PIK3CA
  • Carcinoembryonic Antigen (CEA)
  • Microsatellite Instability High (MSI-H)
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