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Breast cancer is caused by mutations, or damage, to the DNA in breast cells. Exactly what triggers this change is unknown, but many people will spend countless hours trying to figure it out.

What is known is that there are risk factors that may increase your chances of getting breast cancer. Some of them, like age, family history, and dense breasts, can’t be changed. Others are determined by lifestyle factors that can often be controlled.

In the United States, it’s estimated that around 30% of new cancer diagnoses in women will be breast cancer. This makes early detection — and possible prevention — very important. In this article, we’ll go over the potential causes of breast cancer and what you can do about them.

Breast cancer originates in breast tissue. It’s caused by changes, or mutations, in breast cell DNA. These mutations cause cells to grow abnormally and divide quicker than healthy cells do. The abnormal cells accumulate, forming a malignant breast mass, also known as a lump.

Your immune system may be able to successfully fight some abnormal cells. but the ones that continue to grow may spread, or metastasize, throughout the breast to the lymph nodes or other parts of the body.

When breast cancer spreads, the malignant tumors it causes in other places are still referred to as breast cancer.

What exactly triggers DNA changes in breast cells isn’t clear. Two people can have the same or similar risk factors, but only one might develop breast cancer.

Age is the most significant risk factor for breast cancer. Most breast cancer cases are diagnosed in people over 55 years old.

But your genetics and external factors, like smoking, also have an impact. Genetic risk factors can’t be changed, but lifestyle choices that put you at higher risk can be altered.

It’s also likely that for many people, multiple risk factors — both genetic and environmental — have an impact when several are present.

Genetic risk factors


People born with a vagina are at a significantly higher risk for getting breast cancer than those born without one. According to the Centers for Disease Control and Prevention (CDC), only about 1 in every 100 cases of breast cancer diagnosed in the United States is in a man.


You can inherit a gene mutation that puts you at higher risk for breast cancer from either biological parent. About 5 to 10 percent of all breast cancer cases are caused by hereditary gene mutations. The most common type is a mutation in the BRCA1 or BRCA2 gene.

If you have a BRCA1 or BRCA2 gene mutation, your risk for ovarian cancer is also increased.

There are other inherited gene mutations that can increase your risk as well, including:

Family history

If you have several close relatives with breast cancer, you may be more likely to develop it. This is especially true if you have one or more first-degree relatives with breast cancer. A first-degree relative is anyone you share at least 50 percent of your genetics with, like a parent or child.

Having a family history of breast cancer may mean you share the same genetic mutation. But there are other potential explanations here that have nothing to do with genetics.

For example, it may mean you share lifestyle choices that put you at greater risk. It may also be caused by environmental factors, like living in an area where chemical exposure, air pollution, or water pollution levels are high.

Menstruation and menopause

You may be more likely to develop ER-positive breast cancer if you began menstruating at a younger age or started menopause later than usual. This is because there’s a longer period of time when breast cells are affected by estrogen and possibly, progesterone.

Never having given birth also increases your lifetime exposure to estrogen.

If you have given birth, every 12 months that you nurse your child reduces your chance of getting breast cancer by about 4.3 percent.

External risk factors


Smoking cigarettes and using nicotine products modestly increases the risk for breast cancer. The younger you were when you started smoking, the greater your risk. Smoking also increases your risk to a greater degree if you have a family history of the disease.

Alcohol consumption

The International Agency for Research on Cancer has determined that alcohol is a carcinogen that’s causally related to breast cancer risk.

The greater your alcohol intake, the higher your risk may be. But even one drink per day increases risk in both premenopausal and postmenopausal women.

Environmental exposure to toxins

Toxins and chemicals can be found in:

  • soil
  • water
  • dust
  • air
  • personal care products
  • household products
  • packaged foods

Some toxins are known as endocrine disruptors, or endocrine disrupting compounds. These toxins can mimic the effects of estrogen in the body and may increase breast cancer risk. Endocrine disruptors include:

  • BPA (bisphenol A)
  • DDT
  • heavy metals, including arsenic, lead, and mercury
  • phthalates
  • atrazine


Certain foods may increase your risk of breast cancer. Foods to limit or avoid include:

  • fried food
  • sugary foods
  • refined carbohydrates
  • processed meats, including bacon, sausage, and cold cuts


Because fat cells produce estrogen, being overweight or obese can be a significant risk factor — as is having a sedentary lifestyle, which may contribute to increased weight.

Women who’ve previously had breast cancer or are postmenopausal have an even higher risk if they’re overweight or are living with obesity.

Hormone-based medications

Hormonal birth control, including the pill, ring, and IUD, may increase your breast cancer risk slightly. This may be greater if you use hormonal birth control for 5 years or more. If you have a family history of breast cancer, your risk may be higher.

Hormone replacement therapy (HRT) poses a much greater risk. HRT isn’t recommended for symptom relief of menopause in people who have other risk factors for breast cancer.

Know the symptoms

There are symptoms and warning signs of breast cancer that you may notice, especially if you do a monthly self-exam at home.

But many of these signs could be related to natural changes in your body, or of benign (harmless) conditions. This is why it’s important to talk about any changes in your breasts with a healthcare professional.

Signs and symptoms to look for include:

  • lump on the breast, collarbone, or under the arm that doesn’t go away on its own after your period
  • breast pain that doesn’t dissipate after your period
  • nipple discharge
  • nipple or breast dimpling
  • inverted nipple
  • changes to the skin of your breast that include redness, a rash, or being warm to the touch
  • change in breast or nipple shape
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If you’ve never had breast cancer

Early detection won’t stop you from getting breast cancer, but it can help to ensure a better outcome. Talk with a doctor about how often you should get a mammogram. If you have dense breasts, getting regular ultrasounds may also be beneficial.

Adjustments to your lifestyle may also help. These include:

If you’ve already had breast cancer

The following tips may aid with recovery and with avoiding breast cancer recurrence:

  • Keep up with regular screenings.
  • Let your doctor know if you see signs of lymphedema.
  • Eat a diet that’s high in organic fruits and vegetables, and low in red meat, fried food, and processed food. Fish that contain lots of omega-3 fatty acids are also beneficial.
  • Work on maintaining a healthy weight.
  • Be physically active.
  • Try to keep stress levels low. Joining a support group, doing yoga, meditating, or keeping in touch with friends may all help.
  • Consider limiting alcohol use.
  • If you smoke, consider making a plan to quit.

Breast cancer is caused by mutations in breast tissue cells. The underlying risk factors for breast cancer include genetics, environmental toxins, and lifestyle factors, but a definite cause hasn’t been identified.

Make proactive choices to reduce your risk of breast cancer. These include cutting down on smoking and alcohol use, as well as maintaining a healthy weight.