What Is Colon and Rectal (Colorectal) Cancer?

Cancer occurs when cells in the body change and multiply out of control. These cells can form lumps of tissue called tumors. Cancer that forms in the colon is called colon cancer. Cancer that forms in the rectum is called rectal cancer. Because the colon and rectum make up the large intestine, together these cancers are also known as colorectal cancer.

Colorectal cancer is the third most common types of cancer in the United States. The number of deaths from colorectal cancer has decreased, which is attributed to increased screening and polyp removal, and improvements in cancer treatment.

Types of Colon and Rectal Cancer

Adenocarcinoma is a type of cancer that accounts for more than 95% of cancers in the colon and rectum. Other types of colorectal cancer include:

  • Adenocarcinoma: These tumors start in secreting cells in the lining of internal organs. They can form in many different organs, such as the lung or the breast. In colorectal cancer, early tumors often start as small polyps that can grow and become malignant (harmful) tumors. Most colorectal cancers are adenocarcinomas.
  • Carcinoids: Carcinoids are tumors that start in special hormone-producing cells in the intestine. Often, they cause no symptoms at first. Surgery is the typical treatment.
  • Gastrointestinal stromal tumors (GIST): These are tumors that start in specialized cells in the wall of the digestive tract called the interstitial cells of Cajal. These tumors may be found anywhere in the digestive tract, although they rarely appear in the colon. They can be benign (noncancerous) at first, but many turn into cancer. When this happens, they are called sarcomas. Surgery is the usual treatment if the tumor has not spread.
  • Lymphoma: This type of cancer typically starts in a lymph node, which is part of the immune system. It can also start in the colon, rectum or other organs.
  • Sarcoma: This type of tumor starts in blood vessels, muscle or connective tissue in the colon and rectum wall.

Symptoms of Colon and Rectal Cancer

Symptoms of colorectal cancers may resemble other conditions, such as infections, hemorrhoids and inflammatory bowel disease. You may experience symptoms differently and in some cases, no symptoms will be present. The most common symptoms of colorectal cancer include:

  • A change in bowel habits, such as diarrhea, constipation or narrow stools that lasts for more than a few days
  • A feeling that you need to have a bowel movement that is not relieved by doing so
  • Rectal bleeding, dark stools or blood in the stool
  • Cramping or gnawing stomach pain
  • Decreased appetite
  • Vomiting
  • Unintended weight loss
  • Weakness and fatigue

If you experience any of these symptoms, ask your physician or advanced practice provider if you should be screened for colorectal cancer — especially if you are over 45 years old or have a personal or family history of cancer.