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NCCN Guidelines for Patients


Breast Cancer - Early-Stage


, Version 1.2016


Treatment planning

Receptor tests

Receptor tests

Not all breast cancer cells are alike. Cancer cells can

differ by the number or 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 cause changes within the cell. The two types of

receptor tests important for treatment planning are:

Hormone receptor test

Estrogen and progesterone are hormones that are

present in all women. Among some women with

breast cancer, the cancer cells have receptors to

which these hormones attach and cause the cells to

grow in number. As shown in

Figure 2.3

, hormone

receptors are inside of cells and enter the “control

center,” called the nucleus, after binding with

estrogen. However, the growth of cancer cells with

estrogen receptors is usually slower than cancer cells

without these receptors.

Testing for estrogen receptors is important. There

are drugs that can be used to stop hormones from

causing cancer growth. IHC (







is the lab test used by pathologists for hormone


IHC involves applying a stain to cells then looking

at them with a microscope. The stain shows how

many cells have hormone receptors and the amount

of hormone receptors in the cells. If at least 1 out of

every 100 cancer cells stain 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 test

In normal breast cells, there are two copies of the

gene that makes HER2. As shown in

Figure 2.3


HER2 is found within the membrane of cells. It

extends from within the cell through the membrane to

the outside of the cell.

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 gene that

makes HER2. This causes too many HER2 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

learn the amount of HER2 receptors. An IHC score

of 3+ means that the cancer cells have many HER2

receptors. Another test of HER2 is ISH (






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