Breast cancer tends to be more aggressive and difficult to treat when diagnosed earlier in life, but many effective treatments are available. Cases under the age of 40 appear to be increasing slightly in the U.S.

According to the American Cancer Society (ACS), breast cancer accounts for roughly one in three new cases of cancer among women in the United States each year.

Breast cancer is most common in older women, but it also affects those under the age of 40. Although rare, breast cancer can also occur in men.

Read on to learn about breast cancer under the age of 40, including survival rates, treatment options, and more.

Language matters

Sex and gender exist on a spectrum. We use “women” and “men” in this article to reflect the language used in the studies and surveys we reference. However, your gender identity may not align with the terms used below.

Although we typically avoid language like this, specificity is key when reporting on research participants and clinical findings.

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According to a 2018 review, breast cancer is the most common type of cancer among adolescent and young adult women between the ages of 15 to 39 years.

The National Cancer Institute’s Surveillance, Epidemiology, and End Results Program (SEER) reports that around 24 out of 100,000 females between the ages of 15 to 39 years received a diagnosis of breast cancer in 2019.

Breast cancer can also affect adolescent and young men, but it’s very rare in this group.

Factors that affect breast cancer risk

According to the Centers for Disease Control and Prevention (CDC), you’re more likely to develop breast cancer at a young age if:

  • You have close relatives who received a diagnosis of breast cancer at a young age or a diagnosis of ovarian cancer at any age.
  • You have changes in the genes BRCA1 or BRCA2 or other breast cancer genes, or you have close relatives with changes in those genes but you haven’t been tested yourself.
  • You have Ashkenazi Jewish heritage.
  • You received radiation therapy to your breast or chest when you were a child or young adult.
  • You’ve had other breast conditions in the past.
  • Your doctor has told you that you have dense breast tissue.

Talk with your doctor about your personal and family medical history. They can help you assess and manage your risk of breast cancer.

The following factors about your personal health and lifestyle might affect premenopausal breast cancer risk, per a 2017 World Cancer Research Fund report:

  • Height: How tall you are in adulthood is often a reflection of your development when you were younger, including the speed at which you grew and your health and nutrition as a child. Taller people may be at higher risk for premenopausal breast cancer because greater height generally reflects certain patterns in growth and development.
  • Birthweight: Birthweight reflects your growth and nutrition before you’re born and predicts your development later in life. Because of this, higher weight at birth is a marker for increased premenopausal breast cancer risk.
  • Alcohol consumption: Drinking more alcohol is linked to a higher risk for premenopausal breast cancer.
  • Exercise: Practicing vigorous physical activity can protect against premenopausal breast cancer.
  • Breastfeeding or chestfeeding: Breast cancer risk likely gets lower the longer a person lactates, or produces milk.

Estimates show rates of breast cancer under the age of 40 have increased slightly since the early 1990s.

According to SEER, the rate of breast cancer has increased from 20.9 out of 100,000 women in 2000 to 24.3 out of 100,000 women in 2019.

Younger adults tend to develop forms of breast cancer that are more aggressive or harder to treat than those that typically affect older adults.

For example, younger adults are more likely to develop:

  • estrogen receptor (ER)-negative breast cancer
  • progesterone receptor (PR)-negative breast cancer
  • breast cancer with high levels of human epidermal growth factor receptor 2 (HER2)

Younger adults with breast cancer are also more likely to receive a diagnosis after cancer has already spread from the breast to other parts of the body. This makes cancer harder to treat and lowers survival rates.

A 2021 study found that death rates from breast cancer among women under the age of 40 decreased from 1989 to 2010. But since then, death rates from breast cancer among younger women have stopped declining.

Early detection and treatment are important for improving breast cancer survival at any age.

If you develop breast cancer, your doctor’s recommended treatment plan will depend on:

  • the specific type of breast cancer you have, including whether the cancer cells have certain genetic mutations and respond to certain hormones
  • the size and location of the breast cancer tumor(s)
  • whether the cancer has spread, or metastasized, to other parts of your body
  • whether you’ve received cancer treatments in the past
  • whether you’ve gone through menopause
  • your age, overall health, and medical history
  • your treatment preferences and goals

Depending on these factors, your doctor may recommend one or more of the following:

  • surgery
  • radiation therapy
  • hormone therapy
  • chemotherapy
  • targeted therapy
  • immunotherapy

If the cancer has not yet spread to distant parts of your body, your doctor will likely recommend surgery. They will also generally recommend other treatments such as radiation therapy or hormone therapy.

Depending on the type, size, and number of breast cancer tumors, your surgeon may remove the cancer with some of the surrounding tissue or remove your entire breast(s). They may also remove nearby lymph nodes.

You may decide to have breast reconstruction to rebuild or reshape your breast(s) after having the cancer removed.

If cancer has already spread to distant parts of your body, your doctor will likely recommend treatments other than surgery. Often, surgery isn’t an option for breast cancer that has spread to distant parts of your body.

Talk with your doctor to learn more about the potential benefits and risks of different treatment approaches.

Certain treatments for breast cancer can cause short-term or long-term infertility. This includes some types of chemotherapy and hormone therapy for breast cancer.

Some people with breast cancer are also at high risk of developing ovarian cancer. In certain cases, these people may decide to get preventive surgery to remove their uterus, ovaries, or both. This also causes infertility.

Before beginning treatment, consider asking your doctor how it could affect your fertility.

If you’re going to get treatment that could affect your fertility and want to have children in the future, your doctor may recommend fertility preservation.

In fertility preservation, a healthcare professional collects unfertilized eggs or sperm before cancer treatment begins. They may freeze the unfertilized eggs or sperm, or they may fertilize the eggs with sperm and freeze the embryos that result.

At some point, after you finish cancer treatment, you may decide to use the frozen eggs, sperm, or embryos to get pregnant or have a child through surrogacy.

Your outlook with breast cancer depends on the specific type of breast cancer you have, as well as whether it has spread to nearby structures or lymph nodes or distant parts of your body.

The ACS reports the following 5-year relative survival rates for people of all ages with breast cancer:

Status of breast cancer5-year relative survival rate
has not spread beyond the breast99%
has spread to nearby structures or lymph nodes86%
has spread to distant parts of body29%

This means that most people who get a diagnosis of breast cancer before it has spread survive for 5 years or longer. Survival rates decline when the cancer spreads.

Compared with older adults, younger adults are more likely to develop forms of breast cancer that are aggressive or hard to treat. They’re also more likely to receive a diagnosis of breast cancer after the cancer has already spread. As a result, survival rates are lower on average among younger adults with breast cancer.

Survival rates may improve as new treatments become available.

Talk with your doctor to learn more about your specific diagnosis and outlook.

Some types of breast cancer are linked to changes in certain genes that can be passed from parents to children.

Most commonly, these include changes in the BRCA1 and BRCA2 genes. Changes in these genes also raise the risk of ovarian cancer.

If you have a strong family history of breast cancer or ovarian cancer or have close relatives with known genetic mutations that raise the risk of breast cancer, let your doctor know.

They may refer you to a genetic counselor, who might recommend genetic testing. This can help you learn whether you inherited genetic changes that raise your risk of breast cancer.

If you test positive for genetic changes that raise your risk of breast cancer, it may affect your doctor’s breast cancer screening recommendations. They may also prescribe certain treatments to help prevent breast cancer.

There’s no certain way to prevent breast cancer, but healthy lifestyle habits may lower your risk.

If you develop breast cancer, early detection is important for improving your treatment options and outlook.

Mammography screening may help your doctor detect breast cancer early before it causes noticeable symptoms or spreads to other parts of your body. Mammography is a type of X-ray used to examine the breasts.

Prevention

To lower your risk of breast cancer, the ACS recommends:

  • getting regular physical activity
  • maintaining a healthy body weight
  • avoiding or limiting your intake of alcohol

If you have a strong family history of breast cancer or ovarian cancer or you have a known genetic change that raises your risk of breast cancer, your doctor may encourage you to get preventive treatment.

For example, they may prescribe preventive medication to reduce your risk of breast cancer.

In some cases, people at high risk of breast cancer undergo preventive surgery to remove their breasts before breast cancer develops.

Your doctor can help you learn more about the potential benefits and risks of taking preventive medication or getting preventive surgery.

Screening

Different medical organizations have different guidelines for breast cancer screening. Recommendations vary by age, as well as your level of breast cancer risk.

Some organizations such as the ACS and the American College of Radiology (ACR) recommend earlier and more frequent breast cancer screening.

The ACR recommendations focus on women with increased risk:

  • All women, especially Black women and those with Ashkenazi Jewish heritage, should be evaluated for breast cancer risk by age 30.
  • Women with increased risk should undergo mammography screening every year starting at age 30.
  • Women with a history of chest radiation before age 30 should undergo mammography screening every year starting at age 25, or 8 years after the completion of radiation therapy, if this is later than age 25.

Some women may also benefit from other types of breast cancer screening tests, such as contrast-enhanced MRI.

The U.S. Preventive Services Task Force (USPSTF) recommends mammography screening every other year for women ages 50 to 74 years. Women at high risk of breast cancer may benefit from starting mammography screening at a younger age.

The USPSTF is always updating its screening recommendations, so they may change in the future.

Talk with your doctor to learn more about your risk of breast cancer, the potential benefits and risks of breast cancer screening, and when to start screening.

If typical treatment options do not work well for you, your doctor may encourage you to enroll in a clinical trial for breast cancer.

Clinical trials are a type of study that evaluate cancer treatments or other interventions. In many cases, the treatments have not yet received approval from the Food and Drug Administration (FDA).

Participating in a clinical trial may allow you to access an experimental treatment you can’t get elsewhere. It’s possible the treatment may help improve your survival or quality of life with breast cancer. However, it may also cause side effects or carry unknown risks.

To search for breast cancer trials in your region, visit clinicaltrials.gov.

Although breast cancer is most common in older women, it can also affect people under the age of 40.

When breast cancer develops in younger adults, it tends to be more aggressive and harder to treat than in older adults. Early detection and treatment are important for improving survival.

If you have a strong family history of breast cancer or ovarian cancer, your doctor may refer you to a genetic counselor to learn whether you’ve inherited genetic changes that raise your risk of breast cancer.

Talk with your doctor to learn more about your risk of breast cancer and how to manage it through lifestyle changes, mammography screening, or preventive treatment.

If you develop breast cancer, your doctor can help you understand your treatment options and outlook.