The Association of Minimally Invasive Gynecologic Surgeons
…dedicated to safe, state-of-the-art surgery and health life-styles for women of all ages
Do We Know What Causes Breast Cancer?
Although many risk factors may increase your chance of developing breast cancer, it is not yet known exactly how
some of these risk factors cause cells to become cancerous. A woman's hormones somehow stimulate breast
cancer growth. Just how this comes about has not yet been figured out.
Researchers are beginning to understand how certain changes in DNA can cause normal breast cells to become
cancerous. DNA is the chemical that carries the instructions for nearly everything our cells do. We usually resemble
our parents because they are the source of our DNA. However, DNA affects more than our outward appearance.
Some genes (parts of DNA) contain instructions for controlling when our cells grow, divide, and die. Certain genes
that promote cell division are called oncogenes. Others that slow down cell division, or cause cells to die at the
right time, are called tumor suppressor genes. It is known that cancers can be caused by DNA mutations
(changes) that "turn on" oncogenes or "turn off" tumor suppressor genes.
The BRCA genes (BRCA1 and BRCA2) are tumor suppressor genes. When they are mutated, they no longer
function to suppress abnormal growth and cancer is more likely to develop. Certain inherited DNA changes (you
are born with these) can cause an increased risk for developing cancer in people who carry these changes and are
responsible for the cancers that run in some families.
Most DNA mutations related to breast cancer, however, occur in single breast cells during a woman's life rather
than having been inherited. These acquired mutations of oncogenes and/or tumor suppressor genes may result
from radiation or cancer-causing chemicals. So far, studies have not been able to identify any chemical in the
environment or in our diets that is likely to cause these mutations, or a subsequent breast cancer. The cause of
most acquired mutations remains unknown.
Women have already begun to benefit in several ways from recent advances in understanding the genetic basis of
breast cancer. The section, "
What Are the Risk Factors for Breast Cancer?" explains how genetic testing can
identify some women who have inherited abnormal BRCA1, BRCA2, CHEK-2, or p53 tumor suppressor genes.
These women can then take steps to reduce their risk of developing breast cancers and to monitor changes in their
breasts carefully to find cancer at an earlier, more treatable stage. (For more information see the American Cancer
Society documents, "
Medicines to Reduce Breast Cancer Risk" and "Breast Cancer Early Detection.”)
Most breast cancers have several gene mutations that are acquired. That means that these mutations are not
inherited. They develop as part of the cancer.
Tests to identify other acquired changes in oncogenes or tumor suppressor genes (such as p53) may help doctors
more accurately predict the survival outcome of some women with breast cancer. But with the exception of the
HER2 oncogene, these tests have not yet been shown to be useful in making decisions about treatment and are
used only for research purposes.