The only definitive way to determine whether a polyp is cancerous is through a biopsy, according to the National Cancer Institute. Doctors remove polyps that they find during the course of a colonoscopy and biopsy them to see if cancerous tissue is present.
A colon polyp develops from tissue inside the large intestine. Some polyps are shaped like mushrooms on the end of a stem, and others look like bumps lying flat along the wall of the intestine. Polyps come in several different types, and most are benign. However, adenomatous polyps are linked to DNA changes that have the potential to develop into colon cancer. Larger polyps are more likely to contain cancer, notes Drugs.com.
The tendency to produce polyps is genetically transmitted in some. Gardner's syndrome and familial adenomatous polyposis are genetic and potentially cause polyps to grow by the hundreds in the rectum and colon. Surgery to remove the part of the intestine with the growths is necessary to avoid a virtual certainty of cancer by the time the patient reaches middle age, reports Drugs.com.
In many cases, polyps in the colon do not cause any symptoms. If they get large enough, they bleed sometimes, leaving bloody stools. The bleeding can reach the point of causing anemia, an insufficient number of red blood cells, or fatigue, states Drugs.com.