Health A-Z

Medical Content Created by the Faculty of the Harvard Medical School


What Is It?

Colorectal cancer is an uncontrolled growth of abnormal cells in the colon and/or rectum.

Together, the colon and rectum make up the large intestine. The large intestine carries waste from the small intestine and eliminates it through the anus.

Colorectal tumors often begin as small growths (polyps) on the inside of the large intestine. Polyps that are not removed eventually can become cancerous.

Risk Factors

Risk factors for colorectal cancer include:

  • Increasing age

  • Family history of colorectal cancer

  • Personal history of colorectal cancer

  • Personal history of polyps

  • Inflammatory bowel disease, including persistent ulcerative colitis and Crohn's disease

  • Diet low in fiber and high in saturated fat

  • Sedentary lifestyle

  • Race and ethnicity (Alaska natives have the highest risk)

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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