How We Diagnose Rectal Cancer

If you have been diagnosed with rectal cancer, it is important to be seen quickly to start timely treatment. We are committed to seeing patients for an initial diagnosis or second opinion within days. We will assemble the team of specialists that is right for your stage and type of rectal cancer.

Diagnosing Rectal Cancer

If you are diagnosed with rectal cancer, there is often a series of tests to help our team to better understand the extent of the disease to determine the best treatment for you. These tests may be needed to stage the cancer.

  • History and physical exam: Taking a thorough medical history is important to help make a treatment plan appropriate for your body and your goals. Your health care provider examines your body to check general signs of health, including signs of disease, such as lumps and swollen lymph nodes.
  • Blood chemistry studies: Your doctor takes a blood sample to check the amounts of certain substances released into the blood by organs and tissues in the body.
  • Biopsy: If you were diagnosed by a sigmoidoscopy or colonoscopy, a biopsy was likely already taken and sent to a pathologist to look at the cells under a microscope. However, after diagnosis, other biopsies may be needed if abnormalities are found elsewhere in order to test determine the right treatment.
  • Complete blood count (CBC): Your doctor takes a sample of blood to check for the number of red blood cells, white blood cells, and platelets.
  • Carcinoembryonic antigen (CEA) assay: A test that measures the level of CEA in the blood. CEA is released into the bloodstream from both cancer cells and normal cells. When found in higher than normal amounts, it can be a sign of rectal cancer and can be used to determine how a patient's treatment is progressing.
  • Endoscopic ultrasound: An ultrasound probe at the tip of an endoscope allows a doctor to see how deeply the cancer has penetrated and measure the size of the lymph nodes around the rectum.
  • Rigid sigmoidoscopy: A scope inserted through the anus into the rectum measures how far the tumor is from the anus. Either a gastroenterologist or a surgeon usually performs this.
  • Radiology exam: Common radiology procedures include:
    • Chest x-ray: An x-ray of the organs and bones inside the chest. An x-ray is a type of energy beam that can go through the body and onto film, making a picture of areas inside the body.
    • CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, taken from different angles. A computer linked to an x-ray machine makes the pictures.
    • MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed images of areas inside the body.
    • PET scan (positron emission tomography scan): A procedure to find malignant tumor cells in the body. A small amount of radionuclide glucose (sugar) is injected into a vein. The PET scanner rotates around the body and makes a picture of where glucose is being used in the body. Malignant tumor cells show up brighter in the image because they are more active and take up more glucose than normal cells.

When you come to Dana-Farber Brigham Cancer Center's Colon and Rectal Cancer Center, our specialists manage your diagnosis as a team. Our gastroenterology, radiology, and pathology experts specialize in gastrointestinal cancer imaging and diagnostics. This gives us in-depth experience with the disease process and an extraordinary depth of knowledge which can help inform your treatment plan.

Our radiologists are leading cutting-edge research on better diagnostic tools to study cancer and determine how treatments are affecting the cancer.

Radiology Research

Our team regularly publishes its findings about the use of imaging for diagnosis, treatment response, and clinical management of cancer care.

  • Our team has published hundreds of articles on cancer imaging in the past three years.
  • We are investigating new approaches to cancer imaging, including dual energy CT. This research can optimize our understanding of this kind of cancer and help determine whether or not to operate.
  • We are studying the impact of new treatments, such as immunotherapy, and how to best use imaging tools to assess response to newer treatments.

Dana-Farber Brigham Cancer Center pathologists review your pathology slides (even if an outside hospital already reviewed them) to make sure there is agreement on your exact diagnosis.

  • Our pathologists are leaders in the field of gastrointestinal cancer and have more than 500 original publications between them.
  • Pathologists work closely with the Center for Molecular Diagnostics to get a complete picture of your tumor in order to direct the right therapy based on both the tumor type and the molecular features of the cancer.

Precision Cancer Medicine

Clinicians at Dana-Farber Brigham Cancer Center are now armed with specialized tests to create a precise "tumor profile" for each patient's cancer. Learn more about precision cancer medicine.


The process used to find out the extent of the cancer within the rectum or if it has spread to other parts of the body is called staging. This determines your prognosis and your treatment plan.

There are three ways that cancer spreads in the body. When cancer spreads, it is called a metastasis. Cancer can spread through tissue, the lymph system, and the blood:

  • Tissue: The cancer spreads from where it began by growing into nearby areas.
  • Lymph system: The cancer spreads from where it began by getting into the lymph system. The cancer travels through the lymph vessels to other parts of the body.
  • Blood: The cancer spreads from where it began by getting into the blood. The cancer travels through the blood vessels to other parts of the body.

Some staging can be done before having surgery, and other parts of the staging process are done after the cancer is removed from the rectum. During your first meeting with your team at Dana-Farber Brigham Cancer Center, we will discuss with you the best strategy to stage your cancer.

Rectal cancer can be assigned one of these stages:

  • Stage 0: (Carcinoma in situ). Abnormal cells are present in a polyp but have not invaded into the rectal wall.
  • Stage I: Cancer has spread from the innermost layer of the rectal wall (submucosa) or the muscle layer but has not spread to lymph nodes or distant organs.
  • Stage II: Cancer has spread into the fatty tissue around the rectum but has not spread to lymph nodes or distant organs.
  • Stage IIA: Cancer has spread through the muscle layer of the rectum wall to the serosa (the outermost layer).
  • Stage IIB: Cancer has spread through the serosa but not to nearby organs.
  • Stage IIC: Cancer has spread through the serosa to nearby organs.
  • Stage III: Cancer has spread to lymph nodes near the rectum but not distant organs.
    • Stage IIIA: Cancer may have spread through the mucosa (innermost layer) of the rectum wall to the submucosa (layer of tissue under the mucosa) and may have spread to the muscle layer of the rectum wall.
  • Stage IIIB: Cancer has spread through the muscle layer of the rectum wall to the serosa (outermost layer) of the rectum wall or has spread through the serosa but not to nearby organs.
  • Stage IIIC: Cancer has spread through the serosa (outermost layer) of the rectum wall but has not spread to nearby organs. Cancer has spread to at least four, but not more than six, nearby lymph nodes.
  • Stage IV: The cancer has spread to other parts of the body, outside of the rectal area.
  • Stage IVA: Cancer has spread to one organ that is not near the rectum, such as the liver, lung, or ovary, or to a distant lymph node. Cancer may have spread through the rectal wall and to nearby organs or lymph nodes.
  • Stage IVB: Cancer has spread to more than one organ that is not near the rectum or into the lining of the abdominal wall. Cancer may have spread through the rectal wall and may have spread to nearby organs or lymph nodes.

Second Opinions

Get Started

Consultations and Second Opinions

It is important to be seen quickly if you've been diagnosed with rectal cancer so you can start treatment and possibly enter a clinical trial. We provide evaluation and diagnostic services for people who:

  • Have suspected tumors or abnormal test results and want to be evaluated.
  • Have received a diagnosis of cancer and want to be treated at Dana-Farber Brigham Cancer Center.
  • Would like a second opinion, including referring doctors throughout the country.

We regularly consult with patients at all stages of rectal cancer. We perform specialized diagnostics and surgery on patients from around the country, who then return to their local hospitals for further treatment.

Some reasons to consider a second opinion include:

  • To confirm your diagnosis and stage of disease.
  • To determine the optimal therapy.
  • To learn more about your cancer from a specialist who has treated other patients like you.
  • To learn if you're eligible for a clinical trial or targeted gene therapy.

Our team often coordinates with providers at other hospitals to:

  • Conduct specialized scans.
  • Recommend a treatment plan.
  • Perform surgery.
  • Continue in an advisory role.
  • Conduct genetic profiling.
  • Evaluate if a patient may be eligible for a clinical trial.

Phone: 877-442-3324
Online: Complete the Appointment Request Form

Can't travel to Boston? Our Online Second Opinion service lets patients from all over the world receive expert second opinions from Dana-Farber oncologists.

For Referring Physicians

Because you, the referring physician, are an integral part of your patient’s care team, we are committed to collaborating to best care for your patient.

If you are a physician and have a patient with diagnosed or suspected rectal cancer, we look forward to working with you and encourage you to contact us before starting your patient on a treatment regimen. Learn how to refer a patient.