Overview
Triple-negative breast cancer (TNBC) is a fast-growing type of breast cancer. Like other types of breast cancer, TNBC starts as a growth of cells in the breast. What makes TNBC different from other types is that the cancer cells don't use the hormones estrogen and progesterone to help them grow. The cells also don't make much of a protein called HER2.
TNBC tends to happen at a younger age and is more common in black women. It also happens more often in people who have DNA changes that increase the risk of breast cancer.
This type of breast cancer is called triple negative because the cells test negative for estrogen receptors, progesterone receptors and HER2 protein. Healthcare professionals use the results of these tests to make treatment decisions. Having TNBC limits the treatment options, since the cancer won't respond to estrogen blocker therapy to lower hormone levels or treatments that target the HER2 protein.
Compared with other types of breast cancer, TNBC is more likely to be diagnosed at a later stage. The cancer often has grown large or spread to the lymph nodes by the time it is found. Treatment for TNBC often starts with medicines, such as chemotherapy and immunotherapy. These medicines can shrink the cancer to make it easier to remove with surgery. Other treatments might include radiation therapy and targeted therapy.
Types
Triple-negative breast cancer (TNBC) is not a single condition. TNBC is a broad term for breast cancers that test negative for estrogen receptors, progesterone receptors and HER2. TNBC includes several subtypes. This helps explain why two people with TNBC may have cancers that grow, spread or are affected by treatment differently.
The subtypes include, but are not limited to:
- Basal-like 1 and basal-like 2. Most, but not all, TNBC falls into the basal-like group. These cancers are called basal-like because in lab testing they show some of the same features as healthy basal cells on the outer layer of the breast ducts and lobules. Basal-like TNBC often grows quickly.
- Mesenchymal and mesenchymal stemlike. These subtypes show features linked to cell movement. The stemlike subtype also has features linked to stemlike cells and blood vessel growth.
- Immunomodulatory. This subtype shows signs of immune cells inside and around the cancer cells or tumor.
- Luminal androgen receptor. This subtype may use androgen hormone instructions to help cancer cells grow.
- Metaplastic. This rare subtype has cancer cells that, under a microscope, do not look like usual breast cancer cells.
Symptoms
Triple-negative breast cancer (TNBC) may not cause signs or symptoms at first. As it grows, TNBC symptoms are usually the same as most other common breast cancer symptoms. These include:
- A breast lump or thickened area of skin that feels different from the surrounding tissue.
- A nipple that looks flattened or turns inward.
- Changes in the color of the breast skin. On white skin, the breast skin may look pink or red. In people with brown or black skin, the breast skin may look darker than the other skin on the chest or it may look red or purple.
- Change in the size, shape or appearance of a breast.
- Changes to the skin over the breast, such as skin that looks dimpled or looks like an orange peel.
- Peeling, scaling, crusting or flaking of the skin on the breast.
When to see a doctor
TNBC is often a fast-growing cancer. It may be more likely to appear between routine mammograms than other breast cancer types. Make an appointment with a healthcare professional if you notice a change in your breasts. Changes to look for may include a lump, an area of puckered or otherwise unusual skin, a thickened region under the skin, and nipple discharge. Don't wait for your next mammogram to see if the change you found is breast cancer. Report any changes in your breasts even if a recent mammogram showed there was no breast cancer. A healthcare professional may recommend additional imaging.
Causes
The exact cause of triple-negative breast cancer (TNBC) often isn't known. This type of breast cancer is more likely to happen in people who inherit DNA changes that increase the risk of breast cancer, such as BRCA1 and BRCA2. These DNA changes run in families and raise the risk of breast cancer. Not all people with TNBC have these DNA changes. More research is needed to understand what causes this type of breast cancer.
Risk factors
Factors that may increase the risk of triple-negative breast cancer (TNBC) include:
- Age. Compared with other types of breast cancer, TNBC tends to happen at a younger age. It is more common in women under 40. This is different from other types of breast cancer that happen more often in older women.
- Race and ethnicity. Black women have a higher risk of TNBC.
- Inherited DNA changes that increase cancer risk. A family history of changes in the BRCA1 and BRCA2 genes can increase your risk of TNBC and other cancers. However, not everyone with these DNA changes gets cancer.
- Dense breast tissue. Breast tissue is made up of fatty tissue and dense tissue. Dense tissue is made of milk glands, milk ducts and fibrous tissue. If you have dense breasts, you have more dense tissue than fatty tissue in your breasts. Having dense breasts can make it harder to find breast cancer on a mammogram. If a mammogram showed that you have dense breasts, your risk of breast cancer is increased. Talk with your healthcare team about other tests you might have in addition to mammograms to look for breast cancer.
- Oral contraceptive use. Using oral contraceptives for 10 years or more is linked with a higher risk of TNBC.
- Having your first child at a younger age. Having your first child after age 30 may lower the risk of TNBC. This is different from other types of breast cancer in which having a child before age 30 lowers the risk.
- Beginning your period at a younger age. Beginning your period before age 11 increases the risk of TNBC and other types of breast cancer.
Complications
Complications that can happen with triple-negative breast cancer (TNBC) include:
- Cancer that comes back. TNBC can come back after treatment. It also might spread to other parts of the body such as the lungs, liver, brain and bones. The risk is highest in the first few years after treatment. When cancer comes back, healthcare professionals sometimes call it recurrent cancer.
- Infertility. TNBC treatment often involves chemotherapy, which can affect the ability to get pregnant after treatment. If you want to have children in the future, talk about this with your healthcare team. Your team may refer you to a fertility specialist who can explain your options. These options might include freezing eggs, freezing embryos and other ways to preserve fertility.
Sometimes people ask if TNBC can cause ovarian cancer. TNBC itself does not cause ovarian cancer. TNBC and ovarian cancer are linked to changes in BRCA genes.
Prevention
There's no sure way to prevent triple-negative breast cancer (TNBC). But making changes in your daily life may help lower your risk of breast cancer in general. Try to:
- Ask about breast cancer screening. Breast density and family history of breast cancer are linked to TNBC. Talk with your doctor or other healthcare professional about when to begin breast cancer screening. Ask about the benefits and risks of screening. Together, you can decide what breast cancer screening tests are right for you.
- Become familiar with your breasts through breast self-exam for breast awareness. Breast awareness can't prevent breast cancer. But it may help you to better understand the look and feel of your breasts. This might make it more likely that you'll notice if something changes. If there is a new change, a lump or something not typical in your breasts, report it to a healthcare professional right away.
- Drink alcohol in moderation, if at all. If you choose to drink alcohol, limit how often you drink. For overall health, do not drink every day. The less you drink, the better. For breast cancer prevention, there is no safe amount of alcohol.
- Exercise most days of the week. Aim for at least 30 minutes of exercise on most days of the week. If you haven't been active lately, ask a healthcare professional for guidance and start slowly.
- Maintain a healthy weight. Work to maintain a healthy weight. If you need to lose weight, ask a healthcare professional about healthy ways to lower your weight. There is no specific diet linked to preventing TNBC.
- Breastfeeding. Consider breastfeeding if you want to and are able to. If you have a baby, breastfeeding might play a role in helping prevent breast cancer. The longer you breastfeed, the greater the protective effect.
People sometimes wonder if there is a vaccine to protect against TNBC. There currently is no vaccine for TNBC.