Worldwide statistics on breast cancer tell you breast cancer is the most common cancer in women and the second most common cancer overall. In the United States, it is the second most common cancer among women after skin cancer.

What then are the breast cancer causes and risk factors that have made it a global epidemic?

What exactly causes it is still uncertain but certain risk factors that you make prone are ascertained through studies.

What causes breast cancer?

We know that breast cancer develops when some cells in the breast tissue begin to grow rapidly and abnormally. These cells continue to build up to form a lump or tumor. These cancerous cells may then spread into the neighboring breast tissue, to the neighboring lymph nodes, or to other parts of your body. This is called metastasis.

The specific causes of breast cancer are not clear, but breast cancer results due to mutation of the normal breast tissue cells into cancer cells.

It develops due to genetic mutations, which damage the DNA of the cell. These mutations can be related to exposure to hormones such as estrogen, inherited genetic defects, or inherited genes such as the BRCA1 and BRCA2 genes that cause cancer.

The breast cancer 1 (BRCA1) and breast cancer 2 (BRCA2) genes are the genes most commonly affected in hereditary breast cancer

Mutations are most common in the BRCA1 and BRCA2 genes. Generally, women who develop a BRCA1 mutation are at a 72% risk of developing breast cancer during their lifetime.

Breast cancer can either develop in the lobes or the ducts of the breast. Accordingly, it is classified as lobular or ductal carcinoma. Both these types of breast cancers can be noninvasive or invasive.

Noninvasive breast cancer is one that is localized and has not spread. Invasive breast cancer is the type that has spread into the neighboring breast tissue, or to the neighboring lymph nodes or the distant organs of the body by metastasis.

Breast cancer risk factors

Studies have shown that a combination of factors can increase your risk of breast cancer. The two most important factors that increase your risk and over which you have no control at all are of being a woman and getting older. It is found that most breast cancers are found in women who are 50 years or older.

Most women harbor some risk factors, but many of them do not get breast cancer. However, breast cancer can also occur even if none of these factors is present except for being a woman.

The following are the risk factors that make you more prone to developing breast cancer. Some are within your control while over some you have no control.

Risk of gender

Being a woman is the biggest risk factor for developing breast cancer. Breast cancer in women is 100 times more common than breast cancer in men.

The advancing age risk

The risk of breast cancer increases with age and more so after the age of 55 years. Young women are at a lesser risk. Only about 5% of breast cancer cases are seen in women below the age of 40 years. Most breast cancers are diagnosed in women after age 50 years.

About 80% of women diagnosed with breast cancer each year are 45 years or older, and about 43% are 65 years old or above.

Risk evaluation by age:

  • In women between the ages 40 to 50 years, the risk of developing breast cancer is one in 69.
  • Between the ages 50 to 60, that risk increases to one in 43.
  • In the 60 to 70 year age group, the risk further increases to one in 29.
  • In women 70 years and older, the risk is highest at one in 26

Personal history

A previous history of breast cancer makes you more prone to develop breast cancer again in anothet part of the same breast or in the other breast.

If you’ve been diagnosed and treated with breast cancer, you are 3 to 4 times more likely to develop a new cancer in the different part of the same breast or in the other breast. This risk is for new cancer developing and is different recurrence of the previous cancer you had.

Family history

If you have an immediate relative (first degree relative) who has breast cancer, your breast cancer risk increases. By an immediate relative, we mean your father, mother, sister or a daughter. This risk is higher if breast cancer occurred in your relative before the age of 50 years.

Genetic factor

About 5% to 10% of breast cancers are believed to be due to faulty genes. Such families carry mutated genes BRCA1 and BRCA2, which increases their breast cancer risks. A strong family history might suggest that you carry these genes.

But, just one or two elderly family members with breast cancer may not mean that you are carrying these genes. Secondly, having these genes increases your breast cancer risk but does not make it inevitable.

Being obese makes you prone to breast cancer

Obesity is one of the important breast cancer risk factors. Obesity increases estrogen levels in the blood as estrogen is produced by fat cells. Chronic exposure to excess estrogen levels greatly increases your cancer risk.

Secondly, lack of physical activity seen in obese women is another contributory factor. Obesity increases your cancer risk by 1.5 times. This post on obesity and cancer will give you a detailed insight. The risk is high especially during the menopausal period.

Having dense breasts

Dense breasts have more connective tissue than fatty tissue. Women with dense breasts are more prone to develop breast cancer. Another disadvantage is that in dense breasts, it can be difficult to see tumors on a mammogram.

Radiation exposure to the chest

Repeated and overexposure of the chest to radiation as a child or as a young adult before the age of 30 years as in radiotherapy can increase your breast cancer risks later in life. This risk greatly increases especially if radiation exposure occurs when the breast cells are first being formed during the prenatal period or during early adolescence.


Drinking excess of alcohol increases your breast cancer risk. By excess, we mean more than two alcohol units every day for many years. This risk becomes more pronounced in postmenopausal women who consume more alcohol and take estrogen. The risk goes up to almost 40%. This post on Effects of alcohol gives a detailed insight.


As explained in U.S. breast cancer statistics, white women are more prone to developing breast cancer than African American, Hispanics and American Asians. However, black women are more likely to develop an aggressive and advanced-stage breast cancer.

Hormonal risk factors

As estrogen affects the development of the breast cancer, over exposure to estrogen for prolonged periods greatly increases your breast cancer risk. The following cases fall in this category.

  • Women who take oral contraceptives
  • Women who are on hormonal replacement therapy given to treat the certain diseases and to tackle symptoms of menopause

The risk begins to increase when you have been taking hormones for more than five years.

Reproductive and menstrual risk factors

  • Early onset of menstruation before the age of 12 years increases your breast cancer risk.
  • Late onset of menopause after the age of 55 years makes you more prone to breast cancer.
  • Women who have their first child after the age of 35 years are more prone.
  • Women who do not have children and have not lactated are at a higher risk.

Certain lifestyle habits increase your risk

  • Diet. A diet of high fat, low fiber and lacking in vitamin D increases your cancer risk.
  • Smoking. An early start in life coupled with heavy smoking makes you that much more prone to breast cancer.

Having the above breast cancer risk factors does not mean that you are going to have breast cancer. There is a breast cancer risk and it only means you are prone. If you are associated with any of these breast cancer risk factors, you should eliminate them wherever possible.