What is metastatic breast cancer?

Also called stage IV, this is breast cancer that has spread to another body part

More than 10,000 participants form the "Field of Women" to raise funds for Breast Cancer Network Australia (Scott Barbour/Getty Images).

If you’ve heard of cancer, you’ve heard of breast cancer -- in fact, it’s the most commonly diagnosed cancer among American women.

This website provided that statistic, and has more online. For example, do you know about 1 in 8 U.S. women, roughly 12%, will develop invasive breast cancer over the course of her lifetime?

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That’s a lot to digest.

When it comes to the phrase “metastatic breast cancer,” it seems people might not be as familiar with what exactly that means.

We thought we’d break down some questions and answers.

Whether you’ve been diagnosed or perhaps it was a friend or relative -- even if you’re just curious, we’ll help answer some of your questions.

First things first: What is it?

Metastatic breast cancer, also called stage IV, is breast cancer that has spread to another part of the body, most commonly the liver, brain, bones or lungs, according to the website mentioned above. Cancer cells can break away from the original tumor in the breast and travel to other parts of the body through the bloodstream or the lymphatic system, which is a large network of nodes and vessels that works to remove bacteria, viruses and cellular waste products.

The cancer can come back in another part of the body months or years after the original diagnosis and treatment. Nearly 30% of women diagnosed with early-stage breast cancer will develop metastatic disease.

Can someone get diagnosed with metastatic breast cancer when he or she is first diagnosed?

Yes. This just means that the cancer in the breast wasn’t detected before it spread to another part of the body.

“A metastatic tumor in a different part of the body is made up of cells from the breast cancer,” breastcancer.org reads. “So if breast cancer spreads to the bone, the metastatic tumor in the bone is made up of breast cancer cells, not bone cells.”

Does a metastatic diagnosis basically mean the situation is hopeless?

No. But it is understandable if you feel frustrated or overwhelmed.

“Many people continue to live long, productive lives with breast cancer in this stage,” according to the site. “There are a wide variety of treatment options for metastatic breast cancer, and new medicines are being tested every day. More and more people are living life to the fullest while being treated for metastatic breast cancer. While metastatic breast cancer may not go away completely, treatment may control it for a number of years.”

What are the symptoms?

Those vary based on the location of the cancer. With bone metastasis, the most common symptom of breast cancer that has spread to the bone is a sudden, noticeable new pain. In contrast, when breast cancer moves into the lung, it often doesn’t cause symptoms at all. Check here to read up on symptoms and diagnoses.

How do doctors treat metastatic cancer?

Some ways include chemotherapy, surgery, radiation therapy, hormonal therapy or targeted therapy. After a diagnosis, it’s helpful to take all the time you need to gather information and make treatment decisions. This website can help.

We’ll end on this note, with these words from the experts: “Being diagnosed with metastatic breast cancer can be overwhelming. You may feel angry, scared, stressed, outraged, and depressed. Some people may question the treatments they had or may be mad at their doctors or themselves for not being able to beat the disease. Others may deal with diagnosis of metastatic breast cancer in a matter-of-fact way. There is no right or wrong way to come to terms with the diagnosis. You need to do and feel what is best for you and your situation.”

This article was initially published in 2019. It has since been updated.