The ultimate guide to breast cancer

The ultimate guide to breast cancer
Breast cancer is a cancer that forms in the cells of the breasts. Here's what you need to know.
Written by Orchid Team

Medically reviewed by Dr. Ryland J. Gore

  • Dr. Ryland J. Gore, MD MPH FACS, is a board-certified breast surgical oncologist. Dr. Gore completed her general surgery residency at Rush University Medical Center and Cook County Hospital in Chicago, Illinois, and completed her breast surgical oncology fellowship at Maimonides Medical Center in Brooklyn, New York. She practices in Atlanta, Georgia. 

What is breast cancer?

Breast cancer is a cancer that forms in the milk ducts of the glands of the breast. Like other types of cancer, it is caused by cells which begin to divide abnormally. Many breast cancers are detected before any symptoms arise, through mammography. Initial symptoms range from feeling a lump under a breast to breast swelling or redness. While breast cancer does occur in men, it is about 80x more common in women, so this patient guide is focused on breast cancer in females.

What are the risk factors for breast cancer?

  • Age
  • Family history 
  • Genetics
  • Lifestyle choices 

At what age is breast cancer usually diagnosed?

Breast cancer affects over 3.8 million Americans, and 12% of women in the US will be diagnosed in their lifetime. It is usually diagnosed between 55 and 64, with the median age of diagnosis being 62.

How does my age affect my breast cancer risk?

The risk of breast cancer increases with age, from about 0.5% in women <40 to ~4% in women between 60-69, and about a 12% lifetime risk. Higher lifelong levels of estrogen exposure may also increase breast cancer risk; for example, women who begin menstruating at a young age, have a late age at menopause, or women who take long-term hormone replacement therapy after menopause have a higher risk for breast cancer. By contrast, breastfeeding, lower age at first birth, and having children (as opposed to none) is associated with lower levels of breast cancer.

How does my family history affect my breast cancer risk?

There is a substantial genetic component to breast cancer; individuals with a first degree female relative (mother, sister, or daughter) with the disease are twice as likely to be diagnosed than individuals without a family history. The heritability of breast cancer is approximately 31%, based on an analysis of 200,000 twin pairs drawn from the population registries of Denmark, Norway, Sweden, and Finland.

How do my genetics affect my breast cancer risk?

The genetics of breast cancer illustrate both monogenic and polygenic components: there are rarer monogenic variants (such as BRCA1/2) which substantially increase breast cancer risk but there is a polygenic component to breast cancer risk as well, which can sometimes confer risk comparable to monogenic variants. These polygenic scores are still useful for further determining risk among BRCA1/2 carriers.

In addition to BRCA1/2, there are genetic variants in other genes that increase a patient’s risk for developing breast cancer, including TP53, CHEK2, PALB2, PTEN, ATM, STK11 and RAD51C

Is there anything I can do to reduce my child’s genetic risk? 

As explained in the breast cancer whitepaper, genetics plays an important role in determining the risk of breast cancer. Using Orchid’s embryo scoring, you can prioritize the embryo with the lowest genetic risk and reduce their risk of breast cancer.  

However, Orchid’s screening comes with some limitations. Somewhere between 5% and 10% of all breast cancer cases are linked to rare genetic variants in the BRCA1 and BRCA2 genes. Because most of these variants are individually very rare, they are not included in genome-wide association studies for breast cancer and thus they are not captured by our genetic risk score. A low breast cancer GRS is therefore no guarantee for not having an elevated genetic risk for breast cancer. 

However, more than 90% of all breast cancer cases are influenced by genetic risk factors outside of the BRCA1 and BRCA2 genes, which are captured by our breast cancer GRS. 

Any individual with a family history of early-onset breast cancer, multiple relatives with breast cancer, or who has other risk factors, such as a personal or family history of ovarian cancer, should seek guidance from a genetic counselor with expertise in cancer genetics, since they may carry a rare BRCA1/2 variant not captured in Orchid’s GRS.

Is there anything I can do to reduce my risk of breast cancer?

How can I screen for breast cancer?

There are multiple ways to screen for early-stage breast cancer and disagreement in the breast cancer field about when to begin screening. If you have specific questions, you should consult with a primary care physician or breast cancer specialist about screening. The appendix contains more information on different screening guidelines.

Screening for breast cancer is generally done through imaging:

  1. Mammography, a special low-dose x-ray
  2. Breast ultrasound, which confers no radiation exposure
  3. MRI is generally not used for screening, and is only used in the following circumstances: extremely dense breast tissue (as mammography can miss up to 30% of breast cancer cases with increased breast density); history of chest or mantle cell radiation; occult breast cancers detected on MRI but not on standard breast imaging; high-risk patients (carriers of BRCA1/2 or other high-impact monogenic variants mentioned above); calculated lifetime risk of breast cancer >20%; patients diagnosed with breast cancer to evaluate extent of disease.  

These are repeated on a varying basis, depending on which guidelines are followed. 

What actions can increase the risk of breast cancer?

There are some behaviors associated with higher risk of breast cancer, like drinking alcohol, being overweight/obese, and not engaging in regular physical activity. Since radiation exposure can increase the risk of breast cancer, avoiding high radiation exposure is recommended. Avoiding cigarette smoking may help as well.

Are there any ways to reduce the risk of breast cancer?  

By contrast, breastfeeding is associated with lower levels of breast cancer. 

What are the symptoms of breast cancer?

The first noticeable symptoms of breast cancer are changes to the breast including a breast lump or thickening that feels different from the surrounding tissue, change in the size, shape or appearance of a breast, nipple inversion or nipple discharge, and peeling, scaling, or flaking of the pigmented area of skin surrounding the nipple (areola) or breast skin. 

How is breast cancer diagnosed? 

To best plan the appropriate surgery, doctors try to get an accurate diagnosis before surgical intervention. This usually consists of imaging and breast biopsies. The biopsied tissue is examined under a microscope to obtain the type and “grade” of the cancer, and molecular and/or genetic testing is usually performed as well. 

How is breast cancer treated?

The prognosis of breast cancer depends on the stage of disease upon diagnosis. Mammography screening has been shown to lead to earlier detection, with different professional associations recommending different start dates for screening. Several treatments, such as medications (including chemotherapy), surgery, and radiotherapy may be recommended  by a multidisciplinary team, including a medical oncologist, surgical oncologist, and radiation oncologist. 

The prognosis of breast cancer depends mostly on how “advanced” the cancer is, which is determined through imaging and tissue biopsies. These tell the doctor how far the cancer has spread. The patient’s age and the genetics of a cancer may matter as well, but simple models that use only how far a cancer has spread seem to do as well.

What medications are used to treat breast cancer?

In women with a breast cancer diagnosis or high risk of developing breast cancer, there are some medications (tamoxifen, raloxifene, and aromatase inhibitors) that have been used to prevent breast cancer, prevent a new breast cancer, and/or reduce the risk of a breast cancer recurrence. Because many breast cancers appear to grow with estrogen exposure, drugs that interfere with estrogen activity in the breasts reduce the incidence of certain types of breast cancers. The USPSTF, an independent government group that issues recommendations on screening and preventative services, says that doctors should offer women at high risk for breast cancer these drugs.

Once breast cancer is diagnosed, chemotherapy may be prescribed (usually in the setting of stage 4 disease) before surgery to decrease the tumor size or after surgery to reduce the risk of breast cancer recurrence. 

What surgery is used to treat breast cancer?

Lumpectomy (removal of just the breast cancer) or mastectomy (removal of the entire breast) are the standard surgical treatments for breast cancer. In women with very high lifetime risk for breast cancer, such as BRCA1/2 carriers (who may have a 60-90%% risk of breast cancer), some opt for a mastectomy before developing breast cancer (“prophylactic mastectomy”). This reduces the risk of subsequent breast cancer by ~90%.


  1. Breast cancer is a relatively common cancer
  2. While there is debate about what age to start, breast cancer screening is an established practice starting at age 40-50

Where can I learn more?

  1. On cancer screening in general


How is breast cancer screened for?

Breast Cancer Screening Guidelines

Professional Society Recommendations (reproduced below)

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