When you’re diagnosed with cancer, it can feel like you need to learn a whole new language. Doctors use many terms to describe your particular type of cancer. Among those terms are “invasive” and “metastatic.”
When it comes to breast cancer, invasive and metastatic both refer to cancer that has spread from the site in the breast where it first started. But the words have slightly different meanings, and whether your cancer is dubbed invasive or metastatic has implications for how it might be treated.
What Is Invasive Breast Cancer?
Breast cancer usually begins inside the milk ducts or lobules of the breast tissue. Invasive breast cancer has spread from these areas to nearby breast tissue. After invading other healthy parts of the breast, an invasive cancer can travel to nearby lymph nodes.
The two most common types of invasive breast cancer are:
- Invasive ductal carcinoma, which begins in a milk duct and spreads into nearby breast tissue
- Invasive lobular carcinoma, which starts in the lobules of the breast before spreading
Treatment options for invasive breast cancer depend on how advanced your cancer is, as well as your overall health and preferences.
What Is Metastatic Breast Cancer?
Metastatic breast cancer, which includes stage IV breast cancer, is cancer that has spread (metastasized) from the breast to another part of the body. Breast cancers most often metastasize to the liver, brain, bones, or lungs. It happens when breast cancer cells break off a breast tumor and move through the body in the bloodstream or lymph system.
Even though it’s found in a different organ, metastatic breast cancers are still called breast cancers -- and not bone cancers or lung cancers, for instance -- because they started out as breast cells.
Key Differences Between Invasive and Metastatic Breast Cancer
Metastatic breast cancer isn’t a specific type of breast cancer, but is the most advanced stage of breast cancer. Both invasive and metastatic breast cancer have spread beyond the exact point where they started. Invasive breast cancers may have spread within the breast only, or to nearby lymph nodes or tissues, or may have spread to distant body parts. All metastatic breast cancers have spread outside of the breast and nearby lymph nodes to distant body parts. If a cancer is only invasive within the breast, it’s usually easier for doctors to treat than metastatic disease.
Can Breast Cancer Be Both Invasive and Metastatic?
Yes. But that’s not always the case.
Most metastatic breast cancers were invasive breast tumors before traveling to another body part. Many doctors even consider metastatic breast cancer a type of invasive breast cancer that has spread further. This means that everyone who has metastatic disease has invasive breast cancer. Sometimes, a person already has metastatic breast cancer when they are diagnosed, if it wasn’t found before it spread.
But all invasive breast cancers aren’t metastatic. Earlier stage breast cancers may have invaded other parts of the breast or nearby lymph nodes but haven’t spread to further parts of the body.