Breast cancer is a cancer that starts in the tissues of the breast.
Many breast cancers are sensitive to the hormone estrogen. This means that estrogencauses the breast cancer tumor to grow. Such cancers have estrogen receptors on the surface of their cells. They are called estrogenreceptor-positive cancer or ER-positive cancer.
Some women have what is called HER2-positive breast cancer. HER2 refers to a gene that helps cells grow, divide, and repair themselves. When cells (including cancer cells)have too many copies of this gene, they growfaster. Historically, women with HER2-positivebreast cancer have a more aggressive disease and a higher risk that the disease willreturn (recur) than women who do not have this type. However, this may be changing with specifically targeted treatments against HER2.
Causes, incidence, and risk factors
Over the course of a lifetime, 1 in 8 women will be diagnosed with breast cancer.
Risk factors you cannot change include:
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Age and gender — Your risk of developing breast cancer increases as you get older. Most advanced breast cancer cases are found in women over age 50. Women are 100 times more likely to get breast cancer than men.
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Family history of breast cancer — You may also have a higher risk for breast cancer if you have a close relative who has had breast, uterine, ovarian, or colon cancer. About 20 – 30% of women with breast cancer have a family history of the disease.
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Genes — Some people have genes that makethem more likely to develop breast cancer. The most common gene defects are found in the BRCA1 and BRCA2 genes. These genesnormally produce proteins that protect you from cancer. If a parent passes you a defective gene, you have an increased risk for breast cancer. Women with one of thesedefects have up to an 80% chance of getting breast cancer sometime during their life.
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Menstrual cycle — Women who got their periods early (before age 12) or went through menopause late (after age 55) have an increased risk for breast cancer.
Other risk factors include:
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Alcohol use — Drinking more than 1 – 2 glasses of alcohol a day may increase your risk for breast cancer.
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Childbirth — Women who have never had children or who had them only after age 30have an increased risk for breast cancer. Being pregnant more than once or becoming pregnant at an early age reduces your risk of breast cancer.
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DES — Women who took diethylstilbestrol (DES) to prevent miscarriage may have an increased risk of breast cancer after age 40.This drug was given to the women in the 1940s – 1960s.
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Hormone replacement therapy (HRT) — You have a higher risk for breast cancer if you have received hormone replacement therapy with estrogen for several years or more. Obesity — Obesity has been linked to breast cancer, although this link is controversial. The theory is that obese women produce more estrogen, which can fuel the development of breast cancer.
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Radiation — If you received radiation therapy as a child or young adult to treat cancer of the chest area, you have a much higher risk for developing breast cancer. The younger you started such radiation andthe higher the dose, the higher your risk — especially if the radiation was given during breast development.
Breast implants, using antiperspirants, and wearing underwire bras do not raise your risk for breast cancer. There is no evidence ofa direct link between breast cancer and pesticides.
The National Cancer Institute provides an online tool to help you figure out your risk of breast cancer. See: http://www.cancer.gov/bcrisktool
Symptoms
Early breast cancer usually does not cause symptoms. This is why regular breast exams are important. As the cancer grows, symptoms may include:
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Breast lump or lump in the armpit that is hard, has uneven edges, and usually does not hurt
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Change in the size, shape, or feel of the breast or nipple — for example, you may have redness, dimpling, or puckering that looks like the skin of an orange
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Fluid coming from the nipple — may be bloody, clear to yellow, green, and look like pus

Please stay aware!. Go for regular check ups.