NCCN Guidelines for Patients
Stage IV Breast Cancer, Version 1.2014
Breast cancer basics
controlling how cells behave. Changes in genes,
called mutations, cause normal breast cells to
become cancer cells. 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
have grown into the stroma are called “invasive.”
Third, unlike normal cells, cancer cells can break off
from the primary tumor and form secondary tumors.
Secondary tumors may form in the breast or in other
parts of the body. Breast cancer can spread to other
body parts through blood or lymph vessels that are in
Most often, breast cancer spreads through lymph.
Lymph is a clear fluid that gives cells water and food.
It also has white blood cells that fight germs. Lymph
nodes filter lymph and remove the germs. Most of
the lymph in the breast drains to the axillary lymph
nodes found inside the armpit.
See Figure 2.
in the axillary nodes, cancer cells can multiply and
form secondary tumors. Other nearby lymph nodes
include those just inside the ribs near the breast
bone (internal mammary nodes), those right below
the collarbone (infraclavicular nodes), and those right
above the collarbone (supraclavicular nodes).
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.
Illustration Copyright © 2014 Nucleus Medical Media, All rights
Figure 2. Axillary lymph nodes