NCCN Guidelines for Patients
Stage 0 Breast Cancer, Version 1.2014
Breast cancer basics
Cells have a control center called the nucleus.
The nucleus contains special molecules called
chromosomes. Within chromosomes are coded
instructions, called genes, for building new cells
and controlling how cells behave. Changes in
genes, called mutations, cause normal breast cells
to become cancer cells. But what causes genes in
breast cells to change isn’t fully known. Research
has found some risk factors. A risk factor is anything
that increases a woman’s chances of getting breast
cancer. One example of a risk factor is LCIS. Having
had LCIS increases your chances for breast cancer.
Cancer cells don’t behave like normal cells in three
key ways. First, the changes in genes cause cancer
cells to make too many copies of themselves. Normal
cells divide and multiply when new cells are needed,
but otherwise live in a resting state. Normal cells
also die when old or damaged. 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 extend beyond
the walls of lobules or ducts into the stroma. Breast
cancers that haven’t grown into the stroma are called
“noninvasive” and breast cancers that have grown
into the stroma are called “invasive.” DCIS is a
noninvasive breast cancer.
Figure 1. Parts of the breast
Derivative work of Breast Anatomy by Patrick J. Lynch and C. Carl Jaffe, MD available at
commons.wikimedia.org/wiki/File:Breast_anatomy_normal_scheme.png under a Creative
Commons Attribution 3.0 Unported license.
Illustration Copyright © 2014 Nucleus Medical Media, All rights reserved.