Breast cancer: Cause and risk factors

There is still not any definite cause of breast cancer. But research has proven a genetic predisposition along with many environmental risk factors.


Mutation of cells happens over the course of our lifetime. The mutation can happen when cells make a mistake when copying the genetic code before it divides into two cells. Our immune system discovers most of the mutated cells and kills them, so it can take a very long time before there are enough mutations to form a tumor. This is why breast cancer is more common when we get older- the cells have simply had more years to form a tumor. If you inherit a mutated gene, you can get breast cancer at a younger age, but inheriting a mutated gene doesn't necessarily mean that you will get breast cancer. The most commonly mutated genes for breast cancer are the BRCA1 and BRCA2. On average, between 55-65% of women carrying the BRCA1 mutation and 45% of women carrying the BRCA2 mutation have a lifetime risk of getting breast cancer at some stage of their life.

Risk factors causing breast cancer

Since the genetic predisposition doesn't mean you will get breast cancer, there are other reasons for the cancer. These are environmental factors.

-Age: 1 out of 42 women over the age of 50 develops breast cancer.
- Family history: If a close relative has had breast cancer you may have a higher risk as well. Although it should be noted that breast cancer is the most common cancer for women and therefore it can occur in the same family several times by chance, not because of family history.
- Previously diagnosed with breast cancer: per definition you have a higher risk if you have a previous diagnosis.
- Previous benign breast lump: may slightly increase your risk of developing breast cancer.
- Breast density (size): For the simple reason that bigger breasts have more cells that can become cancerous. Dense   breast tissue also makes it more difficult to trust a mammogram since abnormalities are harder to notice.
- Exposure to estrogen: Sometimes estrogen stimulates breast cancer cells to grow.
- Obesity or being overweight: if you are overweight and have gone through menopause, your body starts producing more estrogen, which might increase your chances of developing breast cancer.
- Being tall: this sounds peculiar, but the interaction between genes, hormones and nutrition may play a role in the development of breast cancer.

Last updated: 12/3/18

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