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Colorectal Cancer

Colorectal cancer occurs when abnormal cells grow in the lining of the colon or rectum located at the end of the digestive system. Colorectal cancer grows slowly over time and mostly begins as a polyp (abnormal tissue growth) that is non-cancerous (benign). An uncommon type of polyp, called adenoma, can become cancerous (malignant). The American Cancer Society estimates that about 140,000 colorectal cancer cases and about 50,000 deaths from colorectal cancer occur each year.


A type of cancer called adenocarcinoma accounts for more than 95 percent of cancers in the colon and rectum. There are several other types of cancers that can be found in the colon and rectum:

  • Adenocarcinoma
    Adenocarcinoma is the most common type of colorectal cancer and it represents more than 95 percent of all colon and rectal cancers. It typically starts within the intestinal gland cells that line the inside of the bowel wall.
  • Gastrointestinal carcinoid tumors
    Carcinoid tumors are rare, slow-growing tumors that form in hormone-producing tissues in the lining of the gastrointestinal tract. These tumors account for just one percent of all colorectal cancers, but half of all of the cancers found in the small intestine.
  • Primary colorectal lymphomas
    Lymphomas are cancers that develop in the lymphatic system, which includes the tonsils, adenoids, spleen and thymus. This type usually occurs later in life, is more common in men than women and accounts for about one percent of all colorectal cancers.
  • Gastrointestinal stromal tumors
    Stromal tumors are a rare type of colorectal cancer that starts in a special cell found in the lining of the gastrointestinal tract. More than 50 percent of stromal tumors start in the stomach.
  • Leiomyosarcoma
    Leiomyosarcoma is an infectious tumor that arises from smooth muscle cells. The colon and rectum have three layers of the type of muscle that can be affected. This accounts for about 0.1 percent of all colorectal cancer cases.
  • Melanoma
    Though most commonly associated with the skin, melanomas can occur anywhere, including the colon or rectum. Skin cancer can cause colorectal cancer, this accounts for about two percent of all colorectal cancer cases.
  • Squamous cell carcinoma
    Squamous cells are the skin cells that mostly make up the bowel lining and it is treated in the same way as anal cancer. It is most common for people in their 70’s and it is twice as prevalent in men than women.


Colorectal cancer symptoms do not usually occur in the early stages of cancer. Some symptoms during late stages may include:

  • Diarrhea or constipation.
  • Feeling that your bowel does not empty completely.
  • Blood (dark spots) in your stool.
  • Gas pains or cramps, or feeling full or bloated.
  • Weight loss.
  • Fatigue.
  • Nausea or vomiting.

If you’re experiencing any of these symptoms, consult a

Risk Factors & Prevention

You are at a greater risk for colorectal cancer risk if you:

  • Are over the age of 45.
  • Have a colorectal polyp.
  • Have a family history of colorectal cancer.
  • Have a personal history of colorectal cancer.
  • Have a high-fat diet.
  • Smoke or are exposed to smoke.
  • Have a history of bowel disease (ulcerative colitis or Crohn's disease – an inflammation of the colon).

The causes of colorectal cancer are unknown. Some risk factors such as smoking and diet can be controlled to help prevent colorectal cancer. It’s also important to have a regular screening for colorectal cancer to detect polyps or growths at early stages. Understanding your genetic make-up with genetic counseling can help determine your risk for colorectal cancer.

Digital rectal exam screening recommendations:

45 years of age or older - Annually for men and women.

Colonoscopy screening recommendations:

45 years of age or older - Every 10 years for men and women.

Or Sigmoidoscopy screening recommendations:

45 years of age or older - Every five years for men and women.

Locations Treating Colorectal Cancer