Colorectal Cancer


Colorectal cancer, cancer that begins in the colon or rectum, is a type of intestinal cancer and is the third most common type of cancer in the U.S. for both men and women. At Mercy, you’ll find a team of experts who specialize in the prevention, diagnosis and treatment of colorectal cancer.

What is Colon Cancer?

Colorectal cancer, commonly called colon cancer, occurs when abnormal cells grow in the tissues of your colon or rectum. The disease usually begins as polyps—small growths of cells that could become cancerous. Polyps develop slowly and may not cause any symptoms. Most polyps can be removed during a colonoscopy, which helps reduce your risk of developing colon cancer.

Types of Colorectal Cancer

Colorectal cancer has several types depending on where it’s located. The most common type - adenocarcinoma - develops in the lining of the large intestine. Other types of colon cancer can develop in different parts of the digestive tract and can affect your hormone production, immune system, nervous system, muscles and other tissues. These types are very rare.

Adenocarcinomas of Colon and Rectum

More than 95% of colorectal cancers are adenocarcinomas, which start in mucous-secreting cells in the lining of the colon and rectum. They often begin as polyps (also called adenomas), which can be removed during colonoscopies before they become cancer. Adenocarcinomas typically start in the inner lining of the large intestine but can spread to other layers.

Rare Types of Colorectal Cancers

  • Gastrointestinal carcinoid tumors - these slow-growing tumors form in neuroendocrine cells, which regulate hormone production. They account for about 1% of all colorectal cancers.
  • Gastrointestinal stromal tumors (GISTs) - these tumors develop in nervous system cells that signal the bowel muscles to contract. GISTs are classified as sarcomas or cancers that begin in connective tissues like cartilage, fat, muscles and blood vessels.
  • Primary colorectal lymphomas - these cancers develop in immune cells in the colon or rectum. They account for less than 1% of all colorectal cancers. Risk factors include having a suppressed immune system or inflammatory bowel disease.

Hereditary Types of Colorectal Cancers

While colorectal cancer isn’t generally hereditary, there are a small number of cases caused by gene mutations (changes) passed down in families. The two most common hereditary colorectal cancers are hereditary nonpolyposis colorectal cancer and familial adenomatous polyposis. If you have a strong family history of colon cancer, especially in your first degree relatives please contact your Mercy primary care doctor to discuss genetic testing for colon cancer no matter your age.   

  • Hereditary nonpolyposis colorectal cancer (HNPCC) - also known as Lynch syndrome or cancer family syndrome, HNPCC occurs when very few or no polyps are found. Cancer often appears on the right side of the colon and occurs at a younger age than non-hereditary colon cancers.
  • Familial adenomatous polyposis (FAP) - this rare type of colon cancer is caused by inherited changes in a gene that controls cell growth. It’s characterized by hundreds or thousands of colon polyps, sometimes appearing in the teenage years.

Colorectal Cancer Causes & Risk Factors

While the exact cause of colon cancer is unknown, several factors can increase your risk of developing it. You can reduce some of these risk factors with diet and lifestyle changes.

Controllable Risk Factors

  • Being overweight or obese
  • Frequently eating red or processed meats
  • Lack of physical activity
  • Smoking (especially long term)
  • Heavy alcohol use

Non-Controllable Risk Factors

  • Having a personal history of adenomatous polyps or colon cancer
  • Having a family history of adenomatous polyps or colon cancer, including a parent, sibling or child who had colorectal cancer younger than age 45; two or more family members (parents, brothers, sisters or children) who had it at any age
  • Inheriting gene mutations linked to colon cancer, such as HNPCC or FAP. Most people who inherit these conditions will get colon cancer if they’re not screened and treated.
  • Being over age 50

Colorectal Cancer Symptoms

Colon cancer doesn’t always cause symptoms, especially in the early stages. If you experience symptoms, they may include:

  • A change in bowel habits, including persistent constipation or diarrhea
  • Feeling like your bowel won’t empty completely
  • Bleeding from the rectum with bright red blood
  • Blood in the stool
  • Cramping or abdominal pain
  • Weakness and fatigue
  • Unexplained weight loss
  • Low red blood cell count (anemia) caused by blood loss through the rectum
Diagnosis & Treatment for Colorectal Cancer

If you’re experiencing symptoms or have a higher risk for colorectal cancer, it can be overwhelming. Mercy has the expertise and support you need every step of the way.

Learn about colorectal cancer diagnosis & treatment options. 

View All Results View All Results