What Are the Reasons for Breast Cancer?

Medically Reviewed on 6/10/2022
Breast cancer is a multifactorial disease that can be caused by genetic and environmental factors. Experts are not yet fully aware of what may be the exact reason for breast cancer.
Risk factors or reasons are not a sure indication that one will develop breast cancer.

Breast cancer is a multifactorial disease that can be caused by genetic and environmental factors. Experts are not yet fully aware of what may be the exact reason for breast cancer. The chances of getting breast cancer depend on the person’s age, personal history, genetic factors, and diet.

Risk factors for breast cancer

Risk factors or reasons are not a sure indication that one will develop breast cancer. Some women with breast cancer have no risk factors. However, many women with risk factors never develop the disease.

However, risk factors for breast cancer may include:

  • More than 70% of all breast cancers occur in women aged 50 years or older. Breast cancer is rare in women aged 20-30 years. Breast cancer is also rare in men.
  • Women who previously had breast or ovarian cancer have an increased chance of developing breast cancer.
  • The risk of breast cancer increases if there is a history of breast cancer in the family. Less than 5% of all breast cancers are due to genetics.
  • Being overweight or obese increases the risk of breast cancer. This is because the body’s fat increases levels of the hormone estrogen.
  • Regularly drinking alcohol increases the risk of developing breast cancer.
  • Women who start their periods (menstruation) at a young age or who have menopause at a late age have an increased risk of breast cancer.
  • Breastfeeding lowers the risk of developing breast cancer, probably because it reduces a woman’s total number of menstrual cycles.
  • Oral contraceptives (the pill) cause a slight increase in breast cancer risk. However, this risk gradually decreases after a woman stops taking them.
  • Women taking hormone replacement therapy (HRT) have an increased risk of developing breast cancer, particularly if they take the combined estrogen and progesterone HRT.
  • Women with dense breasts may have the risk of developing breast cancer, meaning there are a lot of ducts, glands, fibrous tissue, and less fatty tissue.
  • In about 5-10% of breast cancer cases, genetic mutations are linked to the disease. For example, women with mutations in the BRCA genes are at increased risk for breast cancer. Some studies show that women with mutations in the BRCA1 gene have a 50-70% chance of getting breast cancer by the age of 70 years, and women with mutations in the BRCA2 gene have a 40-60% chance.

Why would you need an ultrasound on your breast?

A breast ultrasound or a sonomammography may be done for multiple reasons and may be performed as:

  • Routine mammography screening for preventive purposes
  • Conforming the nature of a lump in the breast (cancer or noncancer) after a digital exam.

If a doctor has recommended an ultrasound of the breast, the most possible reasons are:

  • An individual might have dense breast tissue. Dense breast tissue is not abnormal or harmful. However, cancer cells may be hidden in the dense tissue.
  • On an ultrasound, diagnostic radiologists may distinguish cancer cells in dense breast tissue, which is otherwise not detectable through a mammogram.
  • Dense tissue increases their risk of breast cancer and makes mammogram results harder to read.
  • Ultrasound uses sound waves that bounce off tissue. Different tissue makes different echo patterns and through this, any cancer cells or tissue may be detected.
  • The ultrasound focuses on that dense tissue and shows what lies within it.
  • Though a needle biopsy is still the only way to know for sure about the type of cancer, the ultrasound prompts if there is a suspicious mass within regular dense tissue.
  • Screening ultrasound and biopsy of the lump are done when the lump is noticed and to confirm if the lump is cancer or aggressive.


A lump in the breast is almost always cancer. See Answer

What is the newest treatment for breast cancer?

Targeted therapies are a newer form of breast cancer treatment. They can be used alone or along with other therapies. Targeted therapies directly target cancer cells or specific processes that contribute to the growth of cancer cells. Target therapy often has fewer side effects.

  • Monoclonal antibodies: Monoclonal antibodies are special proteins made in the laboratory to treat many diseases, including cancer. These proteins can attach to a specific target on cancer cells. The body can then identify these cancer cells and produce antibodies to kill them, block their growth, or keep them from spreading. Monoclonal antibodies are given by infusion. They may be used alone or to carry drugs, toxins, or radioactive material directly to cancer cells. Monoclonal antibodies may be used in combination with other therapies.
  • Tyrosine kinase inhibitors: These treatments block signals needed for tumors to grow. Tyrosine kinase inhibitors may be used with other anticancer drugs as adjuvant therapy. 
  • Cyclin-dependent kinase inhibitors: This treatment blocks proteins called cyclin-dependent kinases (CDKs), which cause the growth of cancer cells. Combining CDK4/6 inhibitors with hormone therapy may be effective in treating advanced breast cancer.
  • Mammalian target of rapamycin (mTOR) inhibitors: This treatment blocks a protein called mTOR, which may keep cancer cells from growing and prevent the growth of new blood vessels that tumors need to grow.
  • Poly-ADP ribose polymerase (PARP) inhibitors: This treatment blocks deoxyribonucleic acid (DNA) repair and may cause cancer cells to die.

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Medically Reviewed on 6/10/2022
Chalasani P. Breast Cancer. Medscape. https://emedicine.medscape.com/article/1947145-overview

WebMD. Breast Cancer. https://www.webmd.com/breast-cancer/understanding-breast-cancer-basics