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NCCN Guidelines for Patients



Colon Cancer, Version 1.2017

A disease of cells

Your body is made of trillions of cells. Cancer is a

disease of cells. Each type of cancer is named after

the cell from which it derived. Colon cancer is a

cancer of colon cells.

Almost all colon cancers are adenocarcinomas.

Adenocarcinomas are cancers of cells that line

glands and, in the case of colon cancer, make

mucus. Adenocarcinomas of the colon are the focus

of this book.

Cells have a control center called the nucleus.

The nucleus contains chromosomes, which are

long strands of DNA (






cid) tightly

wrapped around proteins.

See Figure 3

. Within

DNA are coded instructions for building new cells and

controlling how cells behave. These instructions are

called genes.

There can be abnormal changes in genes called

mutations. Some types of mutations that are linked

to cancer are present in all cells. Other mutations are

present only in cancer cells. Mutations cause cancer

cells to not behave like normal cells and, sometimes,

to look very different from normal cells.

Cancer’s threat

Cancer cells don’t behave like normal cells in three

key ways. First, cancer cells grow more quickly and

live longer than normal cells. Normal cells grow

and then divide to form new cells when needed.

They also die when old or damaged as shown in

Figure 4

. In contrast, cancer cells make new cells

that aren’t needed and don’t die quickly when old or

damaged. Over time, cancer cells form a mass called

the primary tumor.

The second way cancer cells differ from normal

cells is that they can grow into surrounding tissues.

If not treated, the primary tumor can grow through

the colon wall. They can even grow into nearby

structures. Colon cancers that haven’t grown into the

second layer of the colon wall are called “noninvasive

cancers.” Colon cancers that have grown into the

second layer are called “invasive cancers.”

Third, unlike normal cells, cancer cells can leave

the colon. This process is called metastasis. In this

process, cancer cells break away from the tumor and

merge with blood or lymph. Then, the cancer cells

travel in blood or lymph through vessels to other

sites. Once in other sites, cancer cells may form

secondary tumors and cause major health problems.


Colon cancer basics

A disease of cells


Cancer’s threat