Cancer types Myrisk screens

Breast Cancer

The breast, which is mostly made of fatty tissue, contains ducts and lobes. The lobes are made of smaller sections called lobules. The lobules make up a network within the breast. The lobules end in milk glands, which are tiny bulbs that can make milk. Ducts connect the milk glands, lobules, and lobes.1,2

Breast cancer is a cancer that begins in the cells of the breast. The majority of breast cancer begins in the cells that line the milk ducts and are called ductal carcinomas. Lobular carcinoma begins in the lobules.1,2,3

Carcinoma of the breast can be invasive (or infiltrating) which means the cancer has spread from its starting location into the surrounding breast tissue. Pre-invasive breast cancer, also known as ductal carcinoma in situ (or DCIS) means cancer started in and remains confined to the milk duct. If it is left untreated, however, DCIS may eventually spread to the surrounding tissue and become an invasive breast cancer.1,2,3

Lobular carcinoma in situ (LCIS) is not cancer, though is considered a breast cancer risk factor. LCIS increases the risk for breast cancer in the same breast or opposite breast from where the LCIS is found.1,2,3

In the United States, the average woman has a 12.9% lifetime risk for breast cancer.4 The average male has a risk of <0.1%.5 Most breast cancer cases in women are diagnosed after the age of 50.4 Some hereditary cancer syndromes cause an increased risk for breast cancer.1,2,3

General Risk Factors

  • Personal history of a previous breast cancer
  • Lobular carcinoma in situ (see above)
  • Atypical hyperplasia – abnormal non-cancerous cells in the breast that can be identified during a breast biopsy (tissue sample)
  • Certain benign breast conditions – some breast biopsy findings of overgrowth of cells without atypia can still slightly increase a woman’s breast cancer risk
  • Dense breast tissue – less fatty tissue of the breast (and more of other types of tissues)
  • Beginning menstruation at an early age (before age 12)
  • A late age of menopause (after age 55)
  • Previous radiation treatment to the chest area (between ages 10-30)
  • Exposure to diethylstilbestrol (DES) (a drug containing estrogen given to pregnant women in the 40s, 50s, and 60s to try to prevent miscarriages) – women who were given this drug and women whose mothers were given this drug during their pregnancy are thought to have a slightly increased risk for breast cancer
  • Exposure to estrogen and progesterone (combined hormone therapy) after menopause
  • Use of birth control pills – some studies have suggested that the use of birth control pills (containing somewhat higher hormone dosages than many currently used birth control pills) slightly increases the risk for breast cancer while other studies have suggested that this use does not increase the risk for breast cancer
  • No history of any full-term pregnancies or having a first full-term pregnancy after age 30
  • Family history of cancer – having family members with breast cancer raises the risk of breast cancer, even in absence of a known hereditary cause
  • Diagnosis of a genetic breast cancer predisposition syndrome

As with the vast majority of cancers, there is no confirmed way to completely prevent the development of breast cancer. Maintaining a healthy weight through a healthy diet and exercise, having a history of full-term pregnancies, limiting alcohol intake, and limiting the use of combined hormone replacement therapy after menopause may help decrease the risk for breast cancer.

The drugs tamoxifen and raloxifene can reduce a woman’s risk for breast cancer. A health care provider may offer one of these medications to a woman if she is considered to have a high risk for breast cancer and is considered a good candidate for either of these medications. These drugs are associated with side effects in some women. Doctors may discuss the option of a prophylactic (risk-reducing) mastectomy with women who are found to have a high risk for breast cancer due to a genetic change associated with an increased risk for breast cancer, a strong family history of breast cancer, significant personal medical findings that increase the risk for breast cancer, or a combination of any of these. A prophylactic mastectomy is a surgery that involves the removal of non-cancerous breast tissue in attempt to prevent the formation of breast cancer.

Symptoms of breast cancer can include lumps or thickening of skin in the breast or underarm areas, changes in the size or shape of the breast, dimpling, puckering, scaly, red, or swollen skin on any area of the breast, an inverted (turned inward) nipple, or leakage of fluid (especially if bloody) from the nipple. Breast cancer may also have no symptoms at all.

Women at average risk should be screened by clinical breast exam, which is a manual examination of the breasts by a healthcare provider, as well as a mammogram. The current guidelines from the American Cancer Society (ACS), American College of OB-GYN (ACOG), and the National Comprehensive Cancer Network (NCCN) are detailed in the table below. It can also be helpful for women of any age to practice breast awareness, being familiar with their breasts and reporting any changes to their doctor.

 Clinical Breast Exam

Age to Begin
Clinical Breast Exam


Age to Begin

ACSN/AN/AOffer at 40Every year
Recommend 45+
ACOGOffered 20s-30sEvery 1-3 yearsOffer at 40Every 1-2 years
Offered 40+Every yearRecommend 50+Every 1-2 years
NCCNRecommend 20s-30sEvery 1-2 yearsRecommend 40+Every year
Recommend 40+Every year

Women who are thought to have a lifetime risk for breast cancer of >20% due to a combination of personal risk factors and a family history of breast cancer are recommended to have an annual breast MRI as part of their breast cancer screening.3,7 Patients who have a family history of breast cancer or who have a genetic change that increases the risk for breast cancer may be told by their doctor that they need to begin breast cancer screening before age 40 and undergo additional screening.3,7 If recommended by a doctor, findings on a mammogram, breast MRI, or breast ultrasound can be further examined by fine needle aspiration (use of a thin needle to remove tissue or fluid) or core needle biopsy (use of a wide needle to remove tissue).3,7

If breast cancer is diagnosed following any of the tests above, treatment will depend on the stage of the cancer (how far the cancer has grown or spread). Treatment can include some combination of surgery, chemotherapy and radiation therapy.



  • More than one to two alcoholic drinks a day


  • Being very overweight; having too much body fat after menopause
General Population
Familial Risk
Varies between general population and hereditary risk based on family history and other factors
Hereditary Risk
Up to 87%


  1. American Society of Clinical Oncology: Breast Cancer (
  2. National Cancer Institute: Breast Cancer treatment(
  3. American Cancer Society: Breast Cancer (
  4. SEER Cancer Stat Facts: Female Breast Cancer. National Cancer Institute. Bethesda, MD,
  5. SEER*Explorer: An interactive website for SEER cancer statistics [Internet]. Surveillance Research Program, National Cancer Institute. Available from
  6. ACOG Practice Bulletin No. 179. Breast cancer risk assessment and screening in average-risk women. American College of Obstetricians and Gynecologists. Obstet Gynecol 2017; 130:e1-16.
  7. Bevers TB, et al. NCCN Clinical Practice Guidelines in Oncology®: Breast Cancer Screening and Diagnosis. V1.2019. Available at
  8. Ford D, et al. Risks of cancer in BRCA1-mutation carriers. Breast Cancer Linkage Consortium. Lancet. 1994 343:692-5.