NCCN Guidelines for Patients
Colon Cancer, Version 1.2017
You’ve learned that you have colon
cancer. It’s common to feel shocked and
confused. Part 1 reviews some basics that
may help you learn about colon cancer.
Before learning about colon cancer, it is helpful
to know about the colon. The colon is part of the
digestive system. This system breaks down food for
the body to use.
After being swallowed, food moves through four
organs known as the digestive tract.
See Figure 1
First, food passes through the esophagus and into
In the stomach, food is turned into a liquid. From
the stomach, food enters the small intestine. In the
small intestine, food is broken down into very small
parts. This allows nutrients to be absorbed into the
From the small intestine, food moves into the large
intestine. The large intestine changes unused food
from a liquid into a solid by absorbing water. This
solid, unused food is called feces or stool. The large
intestine also expels stool from the body.
The colon is part of the large intestine. It is almost
5 feet long. Its four parts are the ascending,
transverse, descending, and sigmoid colon.
The wall of the colon has four main layers.
. The inner layer that has contact with stool
is called the mucosa. The mucosa consists of three
sublayers. They are the epithelium, lamina propria,
and muscularis mucosae.
The epithelium absorbs water from stool and makes
mucus. Mucus is a sticky, thick liquid that protects
the colon. It also helps move stool through the colon.
The lamina propria is a thin layer of connective
tissue. The muscularis mucosae is a thin strip of
The second layer of the colon wall is called the
submucosa. It consists of connective tissue, blood
and lymph vessels, and nerve cells. Lymph is a
clear fluid that gives cells water and food. It also has
white blood cells that fight germs. Blood and lymph
drain from colon tissue into vessels that are in the
submucosa and then travel to other sites.
The third layer of the colon wall is called the
muscularis propria. It is mostly made of muscle
fibers. These muscles help move stool through the
The fourth layer is the outer most part of the colon
wall. It consists either of adventitia or serosa.
Adventitia is connective tissue that binds the colon to
other structures. The serosa, also called the visceral
peritoneum, is a membrane.
The serosa contains has a thin layer of connective
tissue. This tissue is called the subserosa. It is
covered by a single row of cells that make fluid. This
fluid allows the colon to move smoothly against other
Colon cancer basics