Colon Cancer
Overview:
Colon and Rectum Cancer
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What is Colon and Rectum Cancer?
What Is Cancer?
What Is Colorectal Cancer?
How Many People Get Colorectal Cancer?
Risk Factors & Prevention
What Causes Colorectal Cancer?
Can Colorectal Cancer Be Prevented?
Early Detection, Diagnosis, Staging
How Is Colorectal Cancer Found?
After the Tests: Staging
Treatment
How Is Colorectal Cancer Treated?
Clinical Trials
Complementary and Alternative Therapies
Questions for Your Doctor
What Are Some Questions I Can Ask My Doctor?
After Treatment
Moving on After Treatment
What's New
What's New In Colorectal Cancer Research?
How Can I Learn More?
How Can I Learn More?
Related Tools & Topics
Prevention & Early Detection
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Overview:
Colon and Rectum Cancer
What Is Colorectal Cancer?
Colorectal
cancer is a term used to refer to cancer that starts in
the colon or rectum. Colon and rectal cancers begin in the
digestive system, also called the GI (gastrointestinal)
system. This is where food is processed to create energy
and rid the body of waste matter.
After
food is chewed and swallowed, it travels down to the stomach.
There it is partly broken down and sent to the small intestine.
The word "small" refers to the diameter of the
small intestine. The small intestine is really the longest
segment of the digestive system. It is about 20 feet long.
The
small intestine continues breaking down the food and absorbs
most of the nutrients. The small intestine joins the large
intestine (large bowel), a muscular tube about five feet
long. The first part of the large bowel, called the colon,
absorbs water and nutrients from the food and also serves
as a storage place for waste matter. The waste matter moves
from the colon into the rectum, the final 6 inches of the
large bowel. From there the waste passes out of the body
through the opening called the anus during a bowel movement.
The
colon has 4 sections, as shown in the picture above. Cancer
can start in any of the four sections or in the rectum.
The wall of each of these sections (and rectum) has several
layers of tissues. Cancer starts in the inner layer and
can grow through some or all of the other layers. Knowing
a little about these layers is helpful because the stage
(extent of spread) of a cancer depends to a great degree
on which of these layers it affects.
Cancer
that starts in the different areas may cause different symptoms.
In most cases, colon and rectum cancers develop slowly over
a period of several years. We now know that most of these
cancers begin as a polyp – a growth of tissue into the center
of the colon or rectum. A type of polyp known as adenomacan
become cancerous. Removing the polyp early may prevent it
from becoming cancer.
Over
95% of colon and rectal cancers are adenocarcinomas. These
are cancers of the cells that line the inside of the colon
and rectum. There are some other, more rare, types of tumors
of the colon and rectum, but the facts given here refer
only to adenocarcinomas.
Colon
and rectal cancer have many features in common and are often
referred to simply as “colorectal cancer.” They are discussed
together here except for the section about treatment. At
that point they will be discussed separately.
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The information on this page has been extracted from http://www.cancer.org/docroot/CRI/CRI_2_1x.asp?dt=10
