What Is Colon and Rectal 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. These cancers are also known as colorectal cancer.

Combined, colon and rectal cancer are the third most common types of cancer in men and women in the United States. The American Cancer Society estimates that about 140,000 colorectal cancer cases and about 50,000 deaths from colorectal cancer occur each year. 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 percent of cancers in the colon and rectum. Other types of colon and rectal 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 start as small polyps that can continue to grow and become malignant tumors. The vast majority of colorectal cancers are adenocarcinomas.
  • 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 do 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.
  • Carcinoids: Carcinoids are tumors that start in special hormone-producing cells in the intestine. Often they cause no symptoms at first. Surgery is the usual treatment.
  • Sarcoma: This type of tumor starts in blood vessels, muscle or connective tissue in the colon and rectum wall.