Breast Cancer

Breast cancer happens when healthy breast cells become abnormal, multiply and form tumors. Most breast cancers are carcinomas that start in milk ducts or milk-producing glands. Most cases are invasive. This means that without treatment, a tumor can spread to other parts of your body.

Breast cancer is one of the most common cancers that affects women. Approximately 1 in 8 women in the United States will develop breast cancer in their lifetime. Although it’s rare, male breast cancers also occur. 

Most people who have breast cancer survive it. Still, what a breast cancer diagnosis means is different for everyone. The cancer type, its stage and your response to treatment are just a few factors that will shape your outlook.

Breast cancer types

There are several types of breast cancer. Knowing the type helps your healthcare provider choose the best treatment. Common types include:

• Invasive ductal carcinoma (IDC): This cancer starts in your milk ducts and spreads to nearby breast tissue. It’s the most common type of breast cancer in the U.S.
• Invasive lobular carcinoma (ILC): This cancer starts in the milk-producing glands (lobules) in your breast and often spreads to nearby breast tissue. It’s the second most common type of breast cancer in the U.S.
• Ductal carcinoma in situ (DCIS): Like IDC, this breast cancer starts in your milk ducts. The difference is that DCIS doesn’t spread beyond them.

Less common breast cancer types include:

• Inflammatory breast cancer (IBC): This fast-growing cancer looks like a rash on your breast.
• Paget’s disease of the breast: This cancer affects the skin of your nipple and may look like a rash.

​Molecular receptor subtypes

During diagnosis, healthcare providers look for receptors on cancer cells to classify them into subtypes. Receptors are protein molecules. Cells with receptors (+) can attach to hormones, like estrogen and progesterone. This makes the cancer grow. High amounts of HER2 protein on cancer cells can also lead to cancer growth.

Breast cancer subtypes are:

• ER-positive (ER+): Has estrogen receptors 
• PR-positive (PR+): Has progesterone receptors
• HR-positive (HR+): Has both estrogen and progesterone receptors
• HER2-positive (HER2+): Has high levels of HER2 protein
• Triple-negative breast cancer (TNBC): Does not have hormone receptors or high levels of HER2 protein (this rare, invasive cancer is aggressive and spreads more quickly than other breast cancer subtypes)

Knowing the subtype helps providers plan treatment. For example, there are drug treatments that can block the receptors, so that hormones can’t attach and cause cancer growth. But this only helps if the cancer cells have the receptors (+).

Symptoms of breast cancer

Many people worry that finding a breast lump means cancer. But breast lumps are also signs of noncancerous breast conditions. Sometimes, the only sign of breast cancer is a suspicious finding on a screening mammogram. This is why routine mammograms are extremely important for all women.

Breast cancer symptoms may include:

• A change in the size or shape of your breast
• A mass or lump, which may feel as small as a pea and hard, like a marble
• A lump or thickening in your breast or armpit that lasts through your menstrual cycle
• Skin that looks scaly, puckered or dimpled, like an orange peel
• Skin that looks red (on light skin) or darker than other parts (on dark skin)
• Nipple discharge that may be bloody or clear
• A nipple that pulls inward

There isn’t just one sign or symptom of breast cancer. This is why it’s important to see a healthcare provider if you notice a change in the look or feel of your breast or nipple.

Breast cancer causes

Breast cancer happens when the genes inside breast cells change (mutate). The mutation causes the cells to grow out of control and form tumors. Medical experts aren’t sure what triggers the change. The cause is likely a mix of the genes you’re born with and factors in your environment.

Risk factors

Many factors may increase your chances of developing breast cancer. They include:

• Age: Most people diagnosed are over 50 years old.
• Sex: Women are much more likely to develop the condition than men.
• Family history: Your breast cancer risk increases if your biological parents, siblings or children also have it.
• Genetics: Up to 1 in 10 women with breast cancer develop the disease because they have inherited genetic mutations. The most common mutations involve the BRCA1 and BRCA2 genes. 
• Lifestyle factors: Tobacco use and alcohol may increase your breast cancer risk.
• Obesity: Obesity, especially after menopause, increases your risk.
• Radiation exposure: Prior radiation therapy — especially to your head, neck or chest — makes you more likely to develop breast cancer.
• Hormone exposure: Long-term exposure to high levels of estrogen or progesterone can increase your risk. This includes getting your first period early or starting menopause late. Exposure can happen through medicines, like some forms of birth control and hormone replacement therapy.

How doctors diagnose this condition

Healthcare providers use the following tests to diagnose breast cancer:

• Breast exam: Your healthcare provider will inspect your breasts and feel for abnormal tissue. This includes feeling around your armpits, where lumps may also form.
• Imaging tests: Mammograms, ultrasounds and MRIs can help providers identify abnormal tissue. Sometimes, these tests help them rule out noncancerous lumps, like cysts.
• Breast biopsy: Your provider will insert a needle into the suspicious area and remove a tissue sample. They’ll test to see if the cells are cancerous. They’ll also test for receptors on cancer cells.

It’s important to know that a breast biopsy doesn’t make the cancer spread and is absolutely needed to make the diagnosis.

Stages of breast cancer

Cancer staging systems help healthcare providers plan treatment and learn your prognosis, or what you can expect after treatment. The most well-known one is called the TNM system. It considers tumor size and location, and whether cancer has spread to lymph nodes or other sites. Providers use this information to stage breast cancer from 0 to IV. Higher numbers mean more advanced disease.

The TNM stages are:

• Stage 0: The disease hasn’t spread from your breast ducts to other parts of your breast. It’s almost always curable.
• Stage I: The disease may have formed a tumor that’s less than 2 centimeters (cm) across. There may be small areas of cancer spread in the lymph nodes in your armpits.
• Stage II: Tumors can measure anywhere between 2 and 5 cm across. The disease may or may not affect nearby lymph nodes. A tumor may be larger than 5 cm if there are no signs of disease in your lymph nodes.
• Stage III: There’s cancer in breast tissue and lymph nodes.
• Stage IV: Cancer has spread to areas like your bones, liver, lungs or brain. This advanced stage is called metastatic breast cancer. It’s hard to treat.

Providers also consider cell features to help them identify the:

• Tumor grade: How abnormal the cancer cells look compared to healthy cells
• Hormone receptor status: If the cells have receptors for estrogen and progesterone
• HER2 status: If the cells have high amounts of HER2 protein

These features may lead your provider to upstage (increase the cancer stage) or downstage the cancer. For example, a Stage II tumor may be downstaged to Stage I if it’s ER+. This is because ER+ breast cancers often have a better prognosis than Stage II cancers without estrogen receptors.

The stage is one of the most important pieces of information about a breast cancer diagnosis. But it involves a lot of factors that are unique to you. And it can be a lot to process. This is why it’s important to ask your healthcare provider to explain what the cancer stage means for your experience.

How is breast cancer treated?

Surgery is the primary breast cancer treatment. The goal is to remove the entire tumor so that no cancer cells remain. Breast cancer surgeries include:

• Mastectomy: This surgery removes your entire breast.
• Lumpectomy: This surgery removes just the lump and a margin of surrounding tissue. Removing the margin helps ensure that no microscopic disease remains.
• Breast reconstruction: After a mastectomy, you may choose to have surgery that reconstructs your breast.

Providers may combine surgery with one or more of the following treatments:

• Radiation therapy: This treatment uses powerful X-rays from a machine to destroy tumors. You may need it before surgery to shrink a tumor or afterward to kill any remaining cancer cells. It may be the main treatment if you’re not healthy enough for surgery.
• Chemotherapy: Chemo uses strong drugs to fight cancer throughout your body. Like radiation therapy, it can destroy cancer cells before or after surgery. It also treats disease that has spread.
• Hormone therapy: These drug therapies prevent hormones from fueling cell growth in breast cancers that involve hormone receptors.
• Targeted therapy: This treatment can prevent the HER2 protein from fueling cancer growth in HER2+ cancers. These therapies may also target other weaknesses in cancer cells.
• Immunotherapy: This treatment is most often used for triple-negative breast cancer. It helps your immune system find and attack cancer cells.

Providers tailor treatment to your needs. For example, they consider factors like the cancer type, its stage, and whether you’re getting treatment for the first time or the cancer has come back after treatment (breast cancer recurrence).

When should I see my healthcare provider?

See a provider if you have a breast change that doesn’t go away after a few days. Most lumps and bumps in your breast aren’t cancer, but they can be. You’ll need a provider to examine you or run tests to know for sure.

What is the survival rate for breast cancer?

Breast cancer survival rates vary based on lots of factors, but most people survive this cancer. According to data that tracked cancer survival from 2016 to 2024 in the U.S., about 92% of women with breast cancer were alive five years after their diagnosis. But the survival numbers vary based on how advanced the disease is:

• Cancer hasn’t spread beyond the breast: 100%
• Cancer has spread to nearby lymph nodes: 87.5%
• Cancer has spread to distant sites: 33.8%

As you think about survival rates, remember that they’re only estimates based on other people’s experiences. If you have questions about your life expectancy, ask your healthcare provider. They’re your best resource because they know your situation.

Is there anything I can do to feel better?

Learning you have breast cancer can feel jarring and scary. But if you’re diagnosed, it may help to know that the odds are in your favor. Right now, more women are being diagnosed with early-stage breast cancer. This means they’re diagnosed when it’s easier to treat. Fewer people are dying of this disease.

Still, one of the best things you can do is to learn as much as you can about your diagnosis. Don’t hesitate to ask your healthcare provider questions. They can help you understand what you’re dealing with.

Can breast cancer be prevented?

You may not be able to prevent breast cancer. But there are things you can do to reduce your breast cancer risk. This includes doing regular breast self-exams so that you can easily detect a change. You should do these exams no matter your sex. Women of average risk should start getting routine mammograms once they turn 40.

Talk to your healthcare provider if you’re concerned about your chances of developing breast cancer. They can walk you through breast cancer risk assessments that help predict how likely it is that you’ll develop this disease. If you’re high risk, they may advise you to:

• Start breast cancer screenings before age 40.
• Have more frequent breast cancer screenings.
• Take medicines that may lower your breast cancer risk.
• Get a prophylactic (preventive) mastectomy.