Colon Cancer (Colorectal Cancer)

  • Medical Author:
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

  • Medical Editor: Jay W. Marks, MD
    Jay W. Marks, MD

    Jay W. Marks, MD

    Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

Colon Cancer Symptoms

Signs and symptoms of colon cancer tend not to be specific. In other words, the signs and symptoms can occur due to a number of different conditions. When colon cancer is detected in its early stages, it may not have even caused symptoms. Symptoms can also vary according to the specific location within the colon where the tumor is located.

Some symptoms and signs of colon cancer are:

  • rectal bleeding or blood in the stool,
  • dark-colored stool,
  • change in bowel habits,
  • change in stool consistency,
  • constipation,
  • diarrhea,
  • narrow stools.
Picture of Colon Cancer

Quick GuideColon Cancer: Symptoms, Signs, Screening, Stages

Colon Cancer: Symptoms, Signs, Screening, Stages

Colon cancer facts

  • Colorectal cancer is a malignant tumor arising from the inner wall of the large intestine (colon) or rectum.
  • Colorectal cancer is the third leading cause of cancer in both men and women in the U.S.
  • Common risk factors for colorectal cancer include increasing age, African-American race, a family history of colorectal cancer, colon polyps, and long-standing ulcerative colitis.
  • Most colorectal cancers develop from polyps. Removal of colon polyps can aid in the prevention of colorectal cancer.
  • Colon polyps and early cancer may have no early signs or symptoms. Therefore, regular colorectal cancer screening is important.
  • Diagnosis of colorectal cancer can be made by sigmoidoscopy or by colonoscopy with biopsy confirmation of cancerous tissue.
  • Treatment of colorectal cancer depends on the location, size, and extent of cancer spread, as well as the health of the patient.
  • Surgery is the most common medical treatment for colorectal cancer.
  • Early-stage colorectal cancers are typically treatable by surgery alone.
  • Chemotherapy can extend life and improve quality of life for those who have had or are living with metastatic colorectal cancer. It can also reduce the risk of recurrence in patients found to have high-risk colon cancer findings at surgery.

What is cancer?

Every day within our bodies, a massive process of destruction and repair occurs. The human body is comprised of about 15 trillion cells, and every day billions of cells wear out or are destroyed. In most cases, each time a cell is destroyed the body makes a new cell to replace it, trying to make a cell that is a perfect copy of the cell that was destroyed because the replacement cell must be capable of performing the same function as the destroyed cell. During the complex process of replacing cells, many errors occur. Despite remarkably elegant systems in place to prevent errors, the body still makes tens of thousands of mistakes daily while replacing cells either because of random errors or because there are outside pressures placed on the replacement process that promote errors. Most of these mistakes are corrected by additional elegant systems or the mistake leads to the death of the newly made cell, and another normal new cell is produced. Sometimes a mistake is made, however, and is not corrected. Many of the uncorrected mistakes have little effect on health, but if the mistake allows the newly made cell to divide independent of the checks and balances that control normal cell growth, that cell can begin to multiply in an uncontrolled manner. When this happens, a tumor (essentially a mass of abnormal cells) can develop.

Tumors fall into two categories: there are benign (noncancerous) tumors and malignant (cancerous) tumors. So what is the difference? The answer is that a benign tumor grows only in the tissue from which it arises. Benign tumors sometimes can grow quite large or rapidly and cause severe symptoms, even death, although most do not. For example, a fibroid tumor in a woman's uterus is a type of benign tumor. It can cause bleeding or pain, but it will never travel outside the uterus and grow as a new tumor elsewhere. Fibroids, like all benign tumors, lack the capacity to shed cells into the blood and lymphatic system, so they are unable to travel to other places in the body and grow. A cancer, on the other hand, can shed cells that can travel through the blood or lymphatic system, landing in tissues distant from the primary tumor and growing into new tumors in these distant tissues. This process of spreading to distant tissues, called metastasis, is the defining characteristic of a cancerous or malignant tumor.

Benign tumor cells often look relatively normal in appearance when examined under the microscope. Malignant or cancerous cells usually look more abnormal in appearance when similarly viewed under the microscope.

Cancer is a group of more than 100 different diseases, much like infectious diseases. Cancers are named by the tissues from which the first tumor arises. Hence, a lung cancer that travels to the liver is not a liver cancer but is described as lung cancer metastatic to the liver, and a breast cancer that spreads to the brain is not described as a brain tumor but rather as breast cancer metastatic to the brain. Each cancer is a different disease with different treatment options and varying prognoses (likely outcomes or life expectancy). In fact, each individual with cancer has a unique disease, and the relative success or lack thereof of treatment among patients with the same diagnosis may be very different. As a result, it is important to treat each person with a diagnosis of cancer as an individual regardless of the type of cancer.


Picture of colon (colorectal) cancer.
Picture of colon (colorectal) cancer.
Medically Reviewed by a Doctor on 4/3/2017

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