Doctors typically categorize breast cancer by stages, numbered 0 to 4.

According to the National Cancer Institute, those stages are defined as the following:

  • Stage 0: This is the first warning sign of cancer. There may be abnormal cells in the area, but they have not spread and can’t be confirmed as cancer yet.
  • Stage 1: This is the earliest stage of breast cancer. The tumor is no bigger than 2 centimeters, although some miniscule cancer clusters may be present in the lymph nodes.
  • Stage 2: This signifies that the cancer has started to spread. The cancer may be in multiple lymph nodes, or the breast tumor is larger than 2 centimeters.
  • Stage 3: Doctors consider this a more advanced form of breast cancer. The breast tumor may be large or small, and may have spread to the chest and/or to several lymph nodes. Sometimes the cancer has invaded the skin of the breast, causing inflammation or skin ulcers.
  • Stage 4: The cancer has spread from the breast to other areas of the body.

Stage 4 breast cancer, also called metastatic breast cancer, is considered the most advanced stage. By this stage, the cancer is no longer curable because it has spread beyond the breast and may be affecting vital organs, like the lungs or brain.

For women who get an initial diagnosis of stage 4 breast cancer, the following are the most common symptoms that will likely occur.

In the early stages of cancer, tumors are typically too small to be seen or felt. That’s why doctors advise mammograms and other types of cancer screening techniques. They can detect early signs of cancerous changes.

Although not all stage 4 cancer will include large tumors, many women will be able to see or feel a lump in their breast. It may exist under the armpit or somewhere else nearby. Women may also feel a general swelling around the breast or armpit areas.

Some types of breast cancer result in skin changes.

Paget’s disease of the breast is a type of cancer that occurs in the nipple area. It’s usually accompanied by tumors inside the breast. The skin may itch or tingle, look red, or feel thick. Some people experience dry, flaky skin.

Inflammatory breast cancer may create changes to skin. The cancer cells block lymph vessels, causing redness, swelling, and dimpled skin. Stage 4 breast cancer may develop these symptoms especially if the tumor is large or involves the breast skin.

Nipple discharge can be a symptom of any stage of breast cancer. Any fluid that comes from the nipple, whether colored or clear, is considered nipple discharge. The fluid may be yellow and look like pus, or it may even look bloody.

The breast might look and feel perfectly normal in the early stages of breast cancer, even though there are cancer cells growing inside it.

At the later stages, people may experience swelling in the breast area and/or in the affected arm. This occurs when the lymph nodes under the arm are large and cancerous. This can block the normal flow of fluid and cause a backup of fluid or lymphedema.

Women may feel discomfort and pain as the cancer grows and spreads in the breast. Cancer cells do not cause pain but as they grow they cause pressure or damage to surrounding tissue. A large tumor can grow into or invade the skin and cause painful sores or ulcers. It can also spread into the chest muscles and ribs causing obvious pain.

Fatigue is the most commonly reported symptom in people with cancer, according to a 2011 study published in the journal Oncologist. It affects an estimated 25 to 99 percent of people during treatment, and 20 to 30 percent of people after treatment.

At stage 4 cancer, fatigue may become more prevalent, making everyday life more difficult.

Stage 4 breast cancer can cause discomfort and pain that interrupts regular sleep.

The Journal of Clinical Oncology published a 2001 study, where researchers noted that insomnia in people with cancer is “a neglected problem.” In 2007, Oncologist published a study that noted that “fatigue and sleep disturbance are two of the most frequent side effects experienced by patients with cancer.” Research now focuses on treatment that helps with insomnia.

Cancer can cause nausea, vomiting, diarrhea, and constipation. Anxiety and lack of sleep can also upset the digestive system.

It can be more difficult to eat a healthy diet as these symptoms occur, setting up a vicious cycle. As women avoid certain foods because of stomach upset, the digestive system may lack the fiber and nutrients it needs to function optimally.

Over time, women may lose their appetite and have difficulty taking in the calories they need. Not eating regularly may cause significant weight loss and nutritional imbalances.

An overall difficulty in breathing, including tightness in the chest and difficulty taking in deep breaths, may occur in stage 4 breast cancer patients. Sometimes this means that the cancer has spread to the lungs, and can be accompanied by a chronic or dry cough.

When cancer spreads to other areas in the body, it can cause specific symptoms depending on where it’s spread. Common places for breast cancer to spread include, the bones, lungs, liver, and brain.

Bones

When cancer spreads to the bone it can cause pain and increase the risk of fractures. Pain may also be felt in the:

  • hips
  • spine
  • pelvis
  • arms
  • shoulder
  • legs
  • ribs
  • skull

Walking may become uncomfortable or painful.

Lungs

Once cancer cells get into the lungs they can cause shortness of breath, difficulty breathing, and a chronic cough.

Liver

It can take a while for symptoms to show up from cancer in the liver.

In the later stages of the disease, it might cause:

Brain

When cancer spreads to the brain it can cause neurological symptoms. These can include:

Make an appointment with your doctor if you are concerned about the symptoms you are experiencing. If you have already been diagnosed with breast cancer, you should tell your medical team if you develop new symptoms.

Even though cancer isn’t curable at this stage, it’s still possible to maintain a good quality of life with regular treatment and care. Tell your care team about any new symptoms or discomfort, so they can help you manage it.

Living with stage 4 cancer can also make you feel anxious and even lonely. Connecting with people who understand what you’re going through can help. Find support from others who are living with breast cancer. Download Healthline’s free app here.