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Breast Cancer Guide

Medically reviewed by Leigh Ann Anderson, PharmD. Last updated on May 9, 2022.

According to the Centers for Disease Control and Prevention (CDC), breast cancer is the leading cause of cancer among women in the U.S. (except for skin cancer). Each year, roughly 255,000 new cases of breast cancer will be diagnosed in women, and about 42,000 women will die. However, today, 9 out of 10 women with breast cancer are still alive five years after the diagnosis due to earlier detection and advanced therapies.

What is Breast Cancer?

Cancer is a group of many related diseases that begin in cells, the body's basic unit of life. The body is made up of many types of cells, and normally, cells grow and divide to produce more cells only when the body needs them. Sometimes, however, cells keep dividing when new cells are not needed. These extra cells form a mass of tissue, called a growth or tumor. There are two types of tumors: benign and malignant.

When cancer arises in breast tissue and spreads outside the breast, cancer cells are often found in the axillary lymph nodes under the arm. If the cancer has reached these nodes, it means that cancer cells may have spread to other parts of the body, including other lymph nodes and other organs, such as the bones, liver, or lungs.

When cancer spreads from its original location to another part of the body, the new tumor has the same kind of abnormal cells and the same name as the primary tumor. For example, if breast cancer spreads to the brain, the cancer cells in the brain are actually breast cancer cells. The disease is called metastatic breast cancer.

What Causes Breast Cancer?

The exact causes of breast cancer are not known. However, studies show that the risk of breast cancer increases with age, and that, along with being a woman, is the greatest risk factor. The disease is very uncommon in women under the age of 35. Most breast cancers occur in women over the age of 50, and the risk is especially high for women over age 60. Breast cancer occurs more often in white and black women compared to Hispanic, Asian/Pacific Islander, or American Indian/Alaska Native women (see Table 1).

Table 1. Female Breast Cancer Rate per 100,000 women

Race Age-Adjusted Rate (per 100,000 women)
White 127.5
Black 121.2
Hispanic Asian/Pacific Islander 101
Asian/Pacific Islander 95.5
American Indian/Alaska Native 65.2

Source: CDC. United States Cancer Statistics: Data Visualizations

Women with the following conditions also have an increased risk for breast cancer:

Other factors associated with an increased risk for breast cancer include:

Many risk factors for developing breast cancer cannot be changed, but some can. Being overweight, excessive alcohol use, taking certain hormones, having a first pregnancy after age 30, never having a baby or never breastfeeding, and smoking are risk factors that may elevate the risk for breast cancer.

It is important to know that many of the women who develop breast cancer have none of the risk factors listed above, other than the risk that comes with growing older. And most women, about 88%, are never diagnosed with breast cancer.

Learn more: What it means to have dense breasts

Screening for Breast Cancer

Breast cancer screening has been shown to decrease the risk of dying from breast cancer, and deaths from breast cancer have decreased over the past few decades. Women can take an active part in the early detection of breast cancer by having regularly scheduled screening mammograms.

Clinical breast exams (performed by health care professionals) and monthly breast self-exams are no longer recommended by expert groups. However, some groups do encourage breast "self awareness", which includes breast cancer education, knowing what is normal for your breasts, and what to do if you notice a change.

A screening mammogram, an X-ray of the breast, is the best tool available for finding breast cancer early, before symptoms appear. Mammograms can often detect a breast lump before it can be felt. If an area of the breast looks suspicious on the screening mammogram, additional diagnostic mammograms, an ultrasound, or a magnetic resonance image (MRI) may be needed. Depending on the results, the doctor may advise the woman to have a breast biopsy.

Recommendations for when to start mammograms and how often to have them vary among leading healthcare organizations. In women aged 50 to 74 with an average risk of breast cancer, most recommendations suggest a screening mammogram every year or every 2 years. These screenings may occur more frequently in higher risk women, or using an ultrasound or MRI plus a mammogram.

Starting at age 40, discuss breast cancer screening with your doctor to determine the best frequency based on your age, family history, and other risk factors. Most guidelines recommend to continue screening mammograms in women with a life expectancy of at least 10 more years.

Mammogram after a COVID-19 vaccine

Temporary swelling in the axillary lymph nodes (of the armpit area) have been noticed after a COVID-19 vaccine in some women. This can interfere with interpreting your mammogram image. In general, experts recommend scheduling your mammogram before a COVID vaccine or 4 to 6 weeks after the vaccine. Talk to your doctor if you are not sure when to schedule your mammogram.

Symptoms of Breast Cancer

Early breast cancer usually does not cause pain, and when breast cancer first develops, there may be no symptoms at all. As the cancer grows, it can cause changes in the breast.

Breast cancer signs or symptoms may include:

Any symptoms such as those listed should be reported to a doctor. Most often, they are not cancer, but it's important to check with the doctor so that any problems can be diagnosed and treated as early as possible.

Related: Breast Changes and Conditions

Diagnosis of Breast Cancer

A doctor may perform one or more breast examinations:

When Cancer Is Found

Breasts are made up of lobules that make breast milk and the ducts that carry the milk to the nipples.

The earliest form of breast cancer is called ductal carcinoma in situ (DCIS), which is breast cancer that has not grow outside of the lining of the breast milk ducts. DCIS cancers still need to be treated as they may grow into surrounding tissue if not treated. The pathologist is able to tell if the cancer is ductal or lobular, and whether it has invaded nearby tissues in the breast (called invasive breast cancer). DCIS may need to be checked for hormone receptors and lymph node involvement.

Lobular carcinoma in situ (LCIS) is a risk factor for developing cancer but is not considered a cancer itself. Other types of rare breast cancer include Paget’s disease of the breast and inflammatory breast cancer.

Most breast cancers are invasive when they are found and they have grown outside the ducts or lobules into the surrounding tissue. Locally invasive breast cancer has only spread within the breast tissue, while metastatic cancer has traveled through the blood or lymph to other areas such as the lungs, bone, or liver.

Certain proteins are tested for by a pathologist once breast cancer is detected. It is important to test for these receptors on the cells so that the most appropriate cancer treatment can be received. Not all breast cancers have hormone receptors.

Other tests (lab tests and x-rays) are sometimes performed to predict the progression of the cancer. Examinations of the bones, liver or lungs may be performed because the breast cancer may spread to these areas.

Learn More: Breast lump: Early evaluation is essential

See also


Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.