How Does Breast Cancer Start?

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Normal breast cells become cancerous when they experience changes or mutations in DNA. You inherit some DNA changes from your parents. These increase your odds of developing breast cancer.

Other risk factors related to your lifestyle can increase your odds of developing breast cancer, too. These include factors like foods you eat and the amount of exercise you regularly get. But no one yet knows how lifestyle risk factors influence normal cells to change into cancer.

Hormones also seem to play a part in development of breast cancer. Scientists do not yet understand how this happens.

Two Kinds of DNA Mutations in Breast Cancer

DNA is a chemical in your cells that makes up your genes. Genes tell your cells how to function. When your DNA mutates, it can cause normal breast cells to become cancer. You inherit or acquire DNA mutations.

Inherited DNA Mutations

Inherited DNA mutations pass down from parents to their children. These mutations are in your body cells when you are born. Some of these mutations increase your cancer risk. Many cancers that run in families come from inherited DNA mutations, just as many children’s and adolescents’ cancers also develop from inherited mutations.

Some inherited DNA mutations greatly increase your risk for some types of cancers. The BRCA genes – BRCA1 and BRCA2 – are important genes responsible for stopping tumor growth. When these genes change they fail to stop abnormal cell growth.

When genetic tests show you have mutations in your BRCA1 or BRCA2 genes or other important genes, you can take important precautions to lower your risk of breast cancer. You can use the information to find cancer at an earlier stage, when it is more easily treated.

Acquired DNA Mutations

Breast cancer-related DNA changes are usually acquired. This means changes in your breast cells take place during your lifetime, not because of mutations passed down from your parents. These breast cancer DNA mutations are caused by radiation, cancer-causing chemicals or other unknown factors.  When you acquire DNA changes in your breast cells, these take place over a period of time and are only in your breast cancer cells.

When your DNA mutates, your genes can then mutate. Genes are responsible for many cell activities, such as when they grow, divide to form new cells or die. When you experience changes in these genes, the changes can cause your cells to stop performing normally. Such changes in genes have been linked to cancer.