Colorectal Cancer: Symptoms and Diagnosis


What Are Typical Colorectal Cancer Symptoms?

Colorectal cancer (CRC) might not cause symptoms immediately and screening is the most effective method to identify and remove polyps before they evolve into malignant disease. Speak to your doctor if you experience one or more of the following symptoms:

  • A change in bowel habits including diarrhea, constipation, or narrowing of stool that persists over a couple of days
  • Constant changing in bowel habits – e.g., feeling like there is bowel movement that is not relieved by passing stool
  • Rectal bleeding with visible red blood
  • Blood in the stool, which can change the appearance of stool to look dark brown or black
  • Abdominal cramping or pain
  • Weakness and fatigue
  • Inexplicable weight loss

It is important to remember that the signs and symptoms of CRC are similar to those found in common bowel conditions that are NOT cancer, such as IBD, ulcers or Crohn’s disease. More information on these signs and symptoms can be found on the American Cancer Society (ACS) and the American Society for Clinical Oncology (ASCO) websites. 

Understanding a CRC Diagnosis

CRC is diagnosed after the onset of symptoms or when a guideline-recommended preventive screening test is conducted. Information on types of screening tests can be found here. In addition to diagnosing CRC, doctors perform additional tests to understand whether the cancer has spread to another area of the body, known as metastasis. Your doctor will consider these factors when choosing an appropriate diagnostic method for you:

  • The primary location of the suspected cancer
  • Your symptoms and signs
  • Your age and health
  • Your medical and family health history
  • The results of your earlier screening tests

Both physical tests and the tests listed below may be used to diagnose CRC. Detailed information on these diagnostic tests can be found on the ASCO website:

  • Colonoscopy
  • Biopsy
  • Molecular testing of the tumor tissue
  • Blood tests
  • CT or CAT scan
  • MRI
  • Ultrasound
  • Chest x-ray to determine if the cancer has spread to the lungs
  • PET or PET-CT scan

After these diagnostic tests are performed, your doctor will review the results and determine whether your clinical symptoms are related to cancer. If the results indicate a cancer diagnosis, these tests will also allow your doctor to stage the cancer. Some additional tests may be performed to characterize the tumor and identify the best treatment options.

More information about the entire diagnostic process and details on the associated tests can be found in this ACS document.

What happens after a CRC Diagnosis?


Following a confirmed diagnosis, your doctor may recommend another series of tests to determine the extent of your cancer—this is called staging. Staging tests include abdominal, pelvic, and lung imaging scans. However, the stage of your cancer may not be fully determined until you undergo exploratory CRC surgery to remove the cancer, in parts or whole.

CRC stages range from 0 (very early CRC) to IV (advanced stage CRC). As a rule of thumb, the lower the number, the less the cancer has spread. A higher number like stage IV, is when CRC is considered to have spread (metastasized) to other sites (organs) the body. The staging system most commonly used for CRC is the American Joint Committee on Cancer (AJCC) TNM System, which is based on:

  • The size of the tumor (T)
  • The spread to the surrounding lymph nodes (N)
  • The spread (metastasis) to distant sites (M)

Detailed information on staging can be found on the ACS website and the staging chapter (pages 30-35) of Cancer.Org CRC PDF.

Understanding Your Pathology Report

A pathologist evaluates tissue (biopsy) samples, including your colon and rectal tissue samples removed during surgery or a biopsy. The findings are then written up as a Pathology Report. It contains important information about your tumor and is used to decide the best treatment option for you. You should request a copy of this report and bring it to your treating doctor to better understand your CRC diagnosis.

Below are a few resources that can help decipher the contents of your Pathology Report:

Speaking to Your Loved Ones About Your Diagnosis

A cancer diagnosis can be extremely overwhelming for you as well as for your family and friends. People often are at loss for words, and do not know how to come to terms with this news. They may feel upset and angry; others may find it easier not to talk about it due to fear of saying the wrong thing or confronting the possibility of losing you.

So, how do you talk about your diagnosis with your loved ones? While there is no standard answer to this question, there are a few things you could do to help break this news to your loved ones. Your feelings about your diagnosis are important. Naturally, you will have many emotions centered around your diagnosis, treatment options, and prognosis. It is perfectly normal to wonder ‘Why me?’ The first step is to admit your feelings about your diagnosis to yourself and to allow yourself to feel the way you do. Only you can decide when you are ready to talk about your cancer and how much you want to share. Then, make a list of the people you would want to share this with. The following resources can help you prepare for this conversation:

Speaking to others about your cancer diagnosis can be overwhelming. You should consider participating in support groups or speak with a trained therapist to gain the comfort you seek.