This page discusses what is known about the development of cancer in the colon or rectum.  No matter where a cancer may develop, the pathways are probably similar, but we have learned a lot specifically about cancer in the colon because of our ability to compare colon polyps to colon cancer.  The discovery of various genetic mutations and the apparent progression from polyps to cancer, has greatly enhanced our knowledge about cancers elsewhere as well.

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Much has been learned about how cancer develops in the colon or rectum.  The mucus cell lining of the intestines is continually renewing itself by continuous cell division, just like skin.  It is easy to understand how important it is for the rate of cell division to be carefully controlled, such that there are just the right number of cells lining the intestine.  The cell division is controlled by some of the genes that are located in the DNA of every cell.  These genes, the “code” for the cells, are reproduced in each new cell.  Usually the information in the gene is reproduced exactly in each daughter cell.  But every once in a while, there is a defect, or mutation, in the code as the new cells are made.  Certain mutations may not make much difference.  But there are some mutations that can alter the regulation of cell growth for all subsequent cell divisions.  We have learned to look for some very specific mutations in colon cells that are known to allow the cells to keep dividing continuously.  Actually, it seems that a combination of mutations is what really underlies the development of a cancer.  So if just one mutation occurs in some cells somewhere in the colon, there may be no cancer.  But if in those mutated daughter cells, there is another specific mutation or two, all the later daughter cells will have the potential to invade into surrounding tissues, and this is basically what constitutes a cancer.

Here is a link to a well done video on how cancer develops.

We now know that cancer in the colon or rectum often begins as a polyp, which is a non-cancerous growth in the lining of the large intestine.  These growths develop because the cells have already had one or more of the mutations described above, but have not yet had a critical mutation that would transform them into cells with the ability to invade surrounding tissues.  So the cells that make up a colon polyp are already halfway there, and our colon cancer prevention strategies are based on this understanding.  We are able to look inside the colon with a lighted scope, and remove these polyps, and thus prevent the possibility of progression to cancer.  More about this later.

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Suggested next pages

Incidence of Colon Cancer
Symptoms and Signs of Colon Cancer
Diagnosis of Colon Cancer

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