Types of Breast Cancer

Breast cancer is a complex disease with many different classifications. Each type of breast cancer is characterized by its unique features and behaviors, such as where it starts, whether or not it’s invasive and what its molecular makeup consists of. Understanding which classifications apply to your diagnosis helps our care team determine your prognosis and build the right treatment plan for you. 

Understanding Breast Cancer Types

Breast cancer can be classified a few different ways: where it started, how far it's spread and its molecular or clinical traits. These aren't competing labels — a single diagnosis often fits into more than one at once, and together they give your care team the full picture needed to build your treatment plan.

 

Most breast cancers begin in either the milk ducts or the milk-producing glands (lobules) of the breast. Rarer types, covered further down, can start in the breast's connective tissue or blood vessels instead. From there, they’re classified as either non-invasive or invasive, depending on how far they've moved beyond where they started.

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Non-Invasive Breast Cancer

Non-invasive breast cancer stays confined to the milk ducts or lobules where it started, without growing into nearby tissue. 

Ductal Carcinoma In Situ (DCIS)

Ductal carcinoma in situ (DCIS) is the only type of breast cancer that falls into the “non-invasive” category. When cancer begins in the milk ducts but hasn’t yet grown into surrounding breast tissue, doctors will classify it as (DCIS). Because it doesn't usually cause a lump or other symptoms, DCIS is often found early through early detection via a routine mammogram. Also called stage 0 breast cancer, DCIS is an early form that is very curable.

Invasive Breast Cancer

Once breast cancer has grown beyond the ducts or lobules into surrounding tissue, it's called invasive breast cancer. Most cases are invasive ductal carcinoma (IDC), which starts in the milk ducts, or invasive lobular carcinoma (ILC), which starts in the lobules instead. Together, these make up the majority of invasive diagnoses, typically staged anywhere from stage I to stage III depending on how far they've spread.

From there, doctors classify invasive breast cancer further by receptor status, presentation, who it affects or its stage, and a single diagnosis can fall into more than one of these at once. For example, someone with inflammatory breast cancer could also test triple-negative, meaning they'd be dealing with both at the same time.

Receptor status: One of the main ways doctors classify invasive breast cancer is by looking for three receptors on the cancer cells: estrogen (ER), progesterone (PR) and HER2. Receptor status matters most for invasive breast cancer, since it determines which treatments will work. However, non-invasive breast cancer cells are sometimes tested to guide decisions about hormone therapy after treatment.

 

  • ER-positive, HER2-negative (ER+/HER2-): The most common subtype. Because these cells have estrogen receptors but not HER2, anti-estrogen therapy, such as tamoxifen, works by blocking or starving the cancer of that hormone.
  • HER2-positive (HER2+): These cells have HER2 on the surface. For HER2-positive breast cancer, treatment includes HER2 inhibitors, drugs built specifically to target that receptor.

Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) gets its name from what it lacks: none of the three receptors above (ER, PR or HER2) are present on the cancer cells. It's less common, making up about 15% of breast cancers, but it's aggressive, and it's more commonly associated with an inherited BRCA1 mutation than other subtypes. Without those receptors to target, fewer treatment options are available, though effective treatments still exist.
Learn more about triple-negative breast cancer >

Inflammatory Breast Cancer

Inflammatory breast cancer (IBC) accounts for less than 5% of all breast cancers, and it's aggressive, meaning it can grow and spread quickly. It's classified by how it presents rather than by receptor status. Rather than causing a lump, it shows up as swelling and redness on the skin of the breast, caused by cancer cells clogging the skin's lymph vessels

Learn more about inflammatory breast cancer >

Male Breast Cancer

Any type of breast cancer described here can occur in men, and most cases are hormone receptor-positive, similar to the most common subtype in women. An inherited BRCA2 mutation carries a higher risk of male breast cancer than BRCA1. Male breast cancer is less common than female breast cancer and typically occurs in older men. Stage-for-stage, the prognosis is the same as it is for women. Men are less likely to catch it early since there's no routine screening the way there is for women, so it's worth talking to your doctor about any changes you notice.

Learn more about male breast cancer >

Metastatic Breast Cancer 

While not technically a distinct type, breast cancer is classified as metastatic if it has spread to other areas of the body. Metastatic breast cancer (MBC) is also called stage IV breast cancer or advanced breast cancer. Similar to chronic conditions like diabetes or high blood pressure, metastatic breast cancer is treatable, though not curable. Depending on its receptor subtype, many new treatments are available to help manage it and improve quality of life

Learn more about metastatic breast cancer >

Other Types of Breast Cancer

Breast cancer can also form in rarer ways, starting outside the ducts or lobules entirely:

 

  • Paget disease of the breast: A cancer that starts in the milk ducts and spreads to the skin of the nipple and areola
  • Angiosarcoma: A rare sarcoma that typically occurs in the skin of a previously radiated breast
  • Mucinous carcinoma: A rare, slow-growing invasive cancer where the tumor cells are surrounded by mucus
  • Metaplastic breast cancer: A rare, often aggressive cancer made up of a mix of cell types not usually found in the breast
  • Phyllodes tumor: A usually benign, though occasionally cancerous tumor that starts in the connective tissue of the breast
  • Lobular carcinoma in situ (LCIS): Not technically a cancer, but a high-risk marker for developing breast cancer, caused by abnormal cells in the lobules of the breast

FAQs: Breast Cancer Types

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