Breast cancer: Full guide

What is breast cancer?

Breast cancer starts when cells in the breast grow out of control. These cells can form a lump, called a tumor. Most breast cancers start in the milk ducts or the milk glands (lobules).

Breast cancer is the most common cancer in women in the US, other than skin cancer. Men can get it too, but this is rare.

Not all breast cancers are the same. Your doctors test the tumor to learn what fuels its growth. These results, plus the stage, guide your treatment plan.

Many people with breast cancer go on to live full lives. This is especially true when it is found early. Treatment for cancer that has spread has also improved a lot. Your care team can tell you what to expect in your own situation.

Types

Hormone receptor positive, HER2 negative (HR+/HER2-)

This is the most common type. The cancer cells use the hormones estrogen or progesterone to grow. Treatment almost always includes hormone therapy (medicine that blocks these hormones).

HER2 positive (HER2+)

These cancer cells make too much of a protein called HER2, which helps them grow fast. Medicines that target HER2 work very well against this type.

Triple-negative breast cancer (TNBC)

The cancer cells do not have hormone receptors or extra HER2. It tends to grow faster. Treatment often uses chemotherapy, and sometimes immunotherapy.

Ductal carcinoma in situ (DCIS)

Abnormal cells are inside the milk ducts but have not spread into nearby breast tissue. It is also called stage 0. Treatment aims to stop it from coming back or turning into invasive cancer.

Invasive ductal carcinoma

This is the most common kind of invasive breast cancer. It starts in a milk duct and grows into the breast tissue around it.

Invasive lobular carcinoma

This cancer starts in the milk glands (lobules). It can be harder to see on a mammogram and is usually hormone receptor positive.

Inflammatory breast cancer

A rare, fast-growing type. The breast may look red, swollen, and warm, and the skin may look like an orange peel. It needs chemotherapy, surgery, and radiation.

Metastatic breast cancer

This means the cancer has spread to other parts of the body, such as bones, liver, lungs, or brain. It is also called stage 4. It is treated as a long-term condition.

Breast cancer in men

Men have a small amount of breast tissue and can get breast cancer. It is almost always hormone receptor positive. Some cases are linked to an inherited BRCA2 gene change.

Tests you may have

Mammogram

An x-ray of the breast. It is used for screening and to look more closely at a lump or change.

Breast ultrasound

Uses sound waves to make pictures. It helps tell if a lump is solid or filled with fluid, and checks lymph nodes in the armpit.

Breast MRI

Uses magnets and a contrast dye to make detailed pictures. It may be used to see how big the cancer is or to screen people at high risk.

Core needle biopsy

A doctor uses a hollow needle to take small pieces of tissue. This is the only way to know for sure if cancer is present. A tiny marker clip is often left behind to mark the spot.

Sentinel lymph node biopsy

During surgery, the surgeon removes the first few lymph nodes the cancer would reach. They are checked for cancer cells. For some small cancers, this step may be skipped.

CT scan, bone scan, or PET scan

These scans look for cancer outside the breast. They are usually not needed for small early cancers. They are used for larger cancers, more lymph node spread, or symptoms.

Genetic testing

A blood or saliva test looks for inherited gene changes, such as BRCA1 or BRCA2. Results can affect treatment and your family's cancer risk. It is offered to most people newly diagnosed.

Genomic tumor tests (such as Oncotype DX or MammaPrint)

These tests look at genes inside the tumor. For some HR+/HER2- cancers, they help show whether chemotherapy would add benefit.

Heart test (echocardiogram)

An ultrasound of the heart. It checks how well your heart pumps before and during some treatments, such as HER2 medicines.

What the stage means

The stage tells how big the cancer is and how far it has spread. It is based on the tumor size, lymph nodes, and whether it has spread to distant organs.

Doctors also use the tumor's grade, hormone receptors, and HER2 status to fine-tune the stage. So two people with the same size tumor may have different stages. Ask your care team to explain yours.

Stage 0

Abnormal cells are only inside the milk ducts (DCIS). They have not spread into the breast tissue.

Stage 1

The tumor is small, 2 centimeters (about 3/4 inch) or less. There may be tiny amounts of cancer in nearby lymph nodes.

Stage 2

The tumor is larger, or cancer has spread to a few lymph nodes in the armpit.

Stage 3

The cancer is called locally advanced. It may be large, involve many lymph nodes, or reach the skin or chest wall. Inflammatory breast cancer is at least stage 3.

Stage 4

The cancer has spread to distant parts of the body, such as bones, lungs, liver, or brain. This is metastatic breast cancer.

Tumor markers and gene tests

Your tumor will be tested for certain markers. These results tell your doctors which medicines are most likely to work.

If the cancer spreads, a new biopsy is often done. The markers can change over time, and this can open new treatment choices.

Estrogen receptor (ER) and progesterone receptor (PR)

If the cancer cells have these receptors, the cancer is hormone receptor positive. Hormone therapy can help slow or stop its growth.

HER2

A protein that helps cells grow. If the cancer has a lot of it, it is HER2 positive, and HER2-targeted medicines can help.

HER2-low and HER2-ultralow

Some cancers have a small amount of HER2. They are not HER2 positive, but certain newer medicines may still work if the cancer spreads.

Ki-67

A measure of how fast the cancer cells are dividing. A higher number means faster growth. It can help decide on extra treatment.

Oncotype DX and MammaPrint

Genomic tests on the tumor. For HR+/HER2- cancer, they estimate the chance the cancer comes back and whether chemotherapy helps.

BRCA1 and BRCA2

Inherited gene changes that raise breast and ovarian cancer risk. If you have one, medicines called PARP inhibitors may be an option. Family members may also want testing.

PIK3CA, AKT1, and PTEN

Gene changes in the tumor that are tested in metastatic HR+ cancer. If found, there are targeted pills made to work against them.

ESR1

A change in the estrogen receptor gene that can appear after hormone therapy. It can make some hormone medicines work less well. Newer pills are designed for it.

PD-L1

A protein tested in metastatic triple-negative breast cancer. It helps show whether immunotherapy may help.

Main treatments

Surgery

Lumpectomy removes the tumor and a rim of normal tissue. Mastectomy removes the whole breast. For most early cancers, lumpectomy plus radiation works as well as mastectomy. Some lymph nodes are usually checked too.

Radiation therapy

Strong x-rays kill cancer cells left after surgery. It is usually given after lumpectomy. Sometimes it is given after mastectomy. Many people now need only 1 to 3 weeks.

Hormone therapy

Pills that block estrogen or lower its levels. Examples are tamoxifen and aromatase inhibitors. They are used for hormone receptor positive cancer. People often take them for 5 to 10 years. Some younger women also get shots to pause the ovaries.

Chemotherapy

Medicines that kill fast-growing cells. It may be given before surgery to shrink the tumor. Or it may be given after surgery to lower the chance the cancer comes back. It is also used for cancer that has spread.

HER2-targeted therapy

Medicines such as trastuzumab and pertuzumab. They attack the HER2 protein. They are used for HER2 positive cancer, often with chemo. In early cancer, they are usually given for about a year.

Immunotherapy

Medicine that helps your immune system fight cancer. Pembrolizumab is used with chemo for many triple-negative cancers. It is used in both early and metastatic cancer.

CDK4/6 inhibitors

Pills such as abemaciclib, ribociclib, and palbociclib. They are added to hormone therapy for metastatic HR+ cancer. Some are also used after surgery for early cancer with a high risk of coming back.

PARP inhibitors

Pills such as olaparib and talazoparib. They are for people with an inherited BRCA1 or BRCA2 change. They are used in some early and some metastatic cancers.

Antibody-drug conjugates

An antibody that targets cancer cells, joined to a chemo medicine. It carries the chemo straight to the cancer cell. Examples are trastuzumab deruxtecan and sacituzumab govitecan.

Bone-strengthening medicines

Medicines such as zoledronic acid or denosumab. They protect bones when cancer has spread to them. Some women past menopause also get them after early breast cancer.

Common side effects and what helps

Fatigue

Feeling very tired, even after rest. Light exercise like walking often helps. Plan activities for when you have the most energy, and accept help.

Nausea and vomiting

Common with some chemotherapy. Take anti-nausea medicine as prescribed, even before you feel sick. Eat small meals and sip fluids often.

Hair loss

Many chemotherapy medicines cause hair loss. Hair usually grows back after treatment. Ask about cooling caps, which may help some people keep more hair.

Infection risk (low white blood cells)

Chemotherapy can lower the cells that fight infection. Wash hands often and avoid sick people. A fever can be serious, so call right away.

Numbness or tingling (neuropathy)

Some chemotherapy can affect nerves in the hands and feet. Tell your care team early. Changing the treatment can keep it from getting worse.

Diarrhea and mouth sores

Some targeted pills and chemotherapy cause these. Your team may give medicine to prevent them. Drink plenty of fluids and use a gentle mouth rinse.

Hot flashes and menopause symptoms

Hormone therapy can cause hot flashes, vaginal dryness, and mood changes. Non-hormone medicines and vaginal moisturizers can help. Ask before using any hormone products.

Joint pain and bone thinning

Aromatase inhibitors can cause achy joints and weaker bones. Staying active helps joint pain. You may have bone density scans and take calcium and vitamin D.

Lymphedema (arm swelling)

Removing or treating lymph nodes can cause swelling in the arm. Tell your team if your arm feels heavy or tight. A lymphedema therapist can teach exercises and fit a sleeve.

Skin changes from radiation

The treated skin may turn red, dry, or sore, like a sunburn. Use the creams your team suggests. Wear soft, loose clothing.

Living with and after breast cancer

After treatment, you will have regular checkups. These are often every few months at first, then less often. You will also have a mammogram each year on any remaining breast tissue.

Routine scans and blood tumor markers are usually not needed if you feel well. Most return of cancer is found because of new symptoms. So tell your team about any new or lasting changes.

If you take hormone therapy, try to take it every day for as long as planned. It works best that way. Tell your team about side effects, since there are often ways to manage them.

Regular exercise and a healthy weight may lower the chance of the cancer coming back. Limiting alcohol also helps. Your team can refer you to programs that fit you.

If you were treated young, ask about fertility, birth control, and pregnancy. Ask about this before treatment starts, if possible.

Metastatic breast cancer is usually not curable, but many people live with it for years. Treatment aims to control the cancer and help you feel well. Palliative care (care focused on comfort and quality of life) can help at any stage.

It is normal to feel worried, sad, or tired. Support groups, counselors, and social workers can help you and your family.