NCCN Guidelines for Patients® | Stage IV Breast Cancer - page 16

NCCN Guidelines for Patients
®
Stage IV Breast Cancer, Version 1.2014
14
2
Treatment planning
Cancer cell tests
Cancer cell tests
Not all breast cancer cells are alike. Cancer cells can
differ by the type of receptors they have. A receptor
is a protein found in the membrane of cells or inside
of cells. Substances bind to the receptors and start
changes within the cell. The two types of receptors
important for treatment planning are:
Hormone receptor test
Estrogen and progesterone are hormones that
increase during puberty in girls causing their breasts
to grow. For some breast cancers, the cancer cells
have a high number of hormone receptors. When
hormones attach to the receptors, the cancer cells
grow and divide forming new cancer cells.
Testing for hormone receptors is important because
for cancer fueled by hormones, there are drugs that
stop hormones from causing cancer growth. IHC
(
i
mmuno
h
isto
c
hemistry) is the lab test that most
pathologists use to see if cancer cells have hormone
receptors. The cancer cells are stained to see the
number of cells with hormone receptors. If at least
1 out of every 100 cancer cells stains positive, the
cancer is called hormone receptor–positive. If fewer
cancer cells stain positive for hormone receptors, the
cancer is called hormone receptor–negative.
HER2 receptor tests
In normal breast cells, there are two copies of
the gene that makes HER2 (
h
uman
e
pidermal
growth factor
r
eceptor
2
). HER2 is found within the
membrane of cells. This type of receptor is called a
surface receptor. When HER2 is activated, it causes
breast cancer cells to grow and divide. Some breast
cancers have cells with more than two copies of the
HER2 gene causing too many HER2s receptors to be
made. Other breast cancers have cells with only two
HER2 gene copies but still too many HER2 receptors
are made.
With too many HER2 receptors, breast cancer cells
grow and divide fast. However, there are drugs to
stop these cancer cells from growing. Due to high
costs and the side effects of these drugs, it is very
important to have tests that correctly show HER2
status. Like for hormone receptors, IHC is used to
count the number of HER2 receptors. An IHC score
of 3+ means that the cancer cells have many HER2
receptors. Another test of HER2 is ISH (
i
n
s
itu
h
ybridization). ISH counts the number of copies of
the HER2 gene. If the cancer cells have too many
HER2 genes or receptors, the cancer is called HER2
positive.
Test results
Some breast cancers have high numbers of
hormone receptors, HER2 receptors, or both. Other
breast cancers have normal numbers of estrogen,
progesterone, and HER2 receptors. In these cases,
the cancer is called triple-negative breast cancer. Be
sure your treatment team explains your test results
and how they will guide treatment. Always ask for a
copy of your test results.
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