How a Cell Becomes a Cancer

Cells are the building blocks of all tissue and organs in the human body. Each cell contains genetic material (DNA) and other elements. DNA controls the growth rate of cells.

Normal cells grow and multiply at a specific rate. Cells that grow and multiply without stopping are called cancerous or malignant. Cancerous cells are not detectable when they first start growing. At a certain point, the cancerous cells continue to multiply and form a mass that can be detected. Abnormal cell growth could go on for years before it is large enough to be detected.

What is Colorectal Cancer?

Colorectal cancer may not be at the forefront of people's minds like other types of cancer, such as breast or prostate cancer. However, colorectal cancer is the second leading cause of cancer deaths in the United States.

Definition of colon cancer: Cancer that forms in the tissues of the colon (the longest part of the large intestine). Most colon cancers are adenocarcinomas (cancers that begin in cells that make and release mucus and other fluids).

Definition of rectal cancer: Cancer that forms in the tissues of the rectum (the last several inches of the large intestine before the anus).

Estimated new cases and deaths from colon and rectal cancer in the United States in 2008:

• New cases: 108,070 (colon); 40,740 (rectal)
  
• Deaths: 49,960 (colon and rectal combined)

(source: National Cancer Institute, Accessed June 2008)

Common Symptoms

Colorectal cancer can be particularly deadly because individuals often do not have symptoms, and those with symptoms often have a form of colon cancer that is less curable. When symptoms do occur, the most common are:

• Rectal bleeding
  
• Blood in the stool or a change in bowel habits
  
• Unexplained weight loss
  
• Constant fatigue
  
• Nausea or vomiting

For resources about colorectal cancer, please visit our Healthwise Colorectal Overview page.

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