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What is 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). The American Cancer Society estimates that about 140,000 colorectal cancer cases and about 50,000 deaths from colorectal cancer occur each year.

What are the types of colorectal cancer?

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 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 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.


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.

What are the symptoms of colorectal cancer?

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 with your Primary Care Physician or a Gastroenterologist.

What causes colorectal cancer?

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 makeup with genetic counseling can help determine your risk for colorectal cancer.

What are the risk factors for colorectal cancer?

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).

How is colorectal cancer diagnosed?

Colorectal Cancer Screening

The most common type of screening for colorectal cancer is a colonoscopy, which is recommended every 10 years for those age 45 years and older. For this test, the doctor uses a long, thin, flexible, video scope to check for polyps or cancer inside the rectum and the colon. Polyps can be found and removed during this procedure.

Digital rectal exam screening recommendations:Colonoscopy screening recommendations:Or Sigmoidoscopy screening recommendations:
45 years of age or older45 years of age or older45 years of age or older
Annually for men and women.Every 10 years for men and women.Every five years for men and women.

Do I need a Colonoscopy?

Colonoscopies have the highest cancer detection success rate. Most colorectal cancers start as polyps, and these polyps and colorectal cancer often don’t have symptoms in their early stages. Without routine colonoscopies, polyps and colorectal cancer often aren’t detected until their later stages when they become harder to treat successfully. A colonoscopy is also the only way polyps can be removed before they turn into colorectal cancer.

Schedule a Colonoscopy

If you are over the age of 45 or have a physician referral, please call the number below to schedule your appointment. If you are under the age of 45, please consult your primary care physician.

Staging System for Colorectal Cancer

The staging system for colorectal cancer is based on:

  • Size of the tumor: how far has the tumor grown into the wall of the colon or rectum
  • Spread to nearby lymph nodes
  • Spread to distant sites: has the cancer metastasized to distant lymph nodes or organs

How is colorectal cancer treated?

Treatment for colorectal cancer is dependent on the stage (range from stages 1 to 4) of the cancer. In lower stage (such as stage 1) colorectal cancers, surgery is usually all that is needed to remove the cancer. In higher stage (such as stage 4) colorectal cancers, a combination of treatments is used and doctors from different specialties work together to treat colorectal cancer.

How can colorectal cancer be prevented?

The most effective way to prevent colorectal cancer is to get routine colonoscopies starting at age 45. Maintaining a healthy diet low in animal fats and high in fruits, vegetables and whole grains, increasing physical activity, limiting alcohol consumption, and avoiding tobacco may reduce the risk of colorectal cancer.

FAQs about colorectal cancer

Is colorectal cancer hereditary?

Colorectal cancer isn’t always genetic, but if a family member has had colorectal cancer, you may be more likely to develop it.

What is a gastroenterologist (GI)?

A gastroenterologist, commonly referred to as a GI doctor, is a physician who specializes in diseases of the digestive system. They also perform colonoscopies.

What can I expect during a colonoscopy?

Learn about what to expect during a colonoscopy here.

What is the difference between a colonoscopy and a sigmoidoscopy?

A colonoscopy examines the entire length of your colon, while a sigmoidoscopy examines only the lower third of your colon.

What is an adenoma? How is it different than a polyp?

An adenoma is a common type of polyp that is benign (noncancerous) but may be a precursor to colorectal cancer. If an adenoma is found during your colonoscopy, it will be surgically removed. If the adenoma becomes cancerous, it is called an adenocarcinoma. Adenocarcinoma is the most common type of colorectal cancer.

I found blood in my stool. Could I have colorectal cancer?

While an early sign of colorectal cancer may be bleeding, there are several different reasons for blood in your stool. Consult with your doctor to receive a correct diagnosis and treatment.

What support and resources does MemorialCare offer for people diagnosed with colorectal cancer?