What Causes Breast Cancer?

It is rare for cancer to be strongly hereditary or genetic. On some level though, all cancer is genetic.

Breast cancer is a complicated disease and there is no single explanation for it. In the vast majority of breast cancer, the cause is likely some genetics, some environmental factors such as exposures to toxins and chemicals, and some of it just bad luck. In most cases we are not able to pinpoint a specific cause, likely because in most cases there is not ONE specific cause to be found, but rather a combination of many different things coming together. In fact, many women with breast cancer have no connection with any known risk factors.

Some of the factors that are known to increase breast cancer risk are:

  • Gender: Breast cancer is almost 100 times more common in women than in men.
  • Age: Our risk of developing breast cancer increases as we get older.
  • Race: Breast cancer is diagnosed more often in Caucasian women than in women of other races. However, African American women have a poorer survival rate compared to white women once diagnosed with cancer. This inequality may be due, in part, to differences in the availability of care and not to genetic factors.
  • Family history: A family history of breast cancer increases a woman’s risk of developing breast cancer. How many people are affected in her family, how old they were when they were diagnosed, and how closely they are related to her all will influence how much the risk for cancer is increased.
  • Reproductive/Hormonal History: Having no children, having your first child later in life, early menstruation (before age 12) or late menopause (after age 55) increases the lifetime risk of breast cancer
  • Previous History of Breast Cancer: Women diagnosed with breast cancer in one breast have an increased risk of being diagnosed with breast cancer in the other breast in the future.
  • Certain Benign (Noncancerous) Breast Findings: such as lobular carcinoma in situ (LCIS) can increase lifetime risk for breast cancer.
  • Hereditary Predisposition: Inherited mutations (changes) in specific genes increase the risk for breast cancer. In certain situations genetic testing may be able to clarify if there is an inherited predisposition in an individual or family.
  • Dense Breast Tissue: Increases the risk of breast cancer and also makes detection more difficult.
  • Lack of Physical Activity: An inactive lifestyle increases the risk of breast cancer.
  • Alcohol Consumption: The more alcohol consumed, the more the risk is increased. Most current studies recommend women limit their intake to no more than one serving of alcohol a day, but even this amount will increase breast cancer risk, as alcohol can affect estrogen levels in the body.
  • Obesity or Being Overweight: Individuals with an unhealthy proportion of body fat have an increased risk of breast cancer and decreased survival rates after diagnosis.
  • Hormone Replacement Therapy (HRT): HRT involves taking female sex hormones when a woman’s ovaries stop producing such hormones after menopause. HRT involves only estrogen, while combined HRT includes both estrogen and progesterone. Both treatments increase the risk of cancer but combined HRT has been linked to a higher risk for breast cancer.

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