Types of Breast Cancer
Invasive Vs. Non-Invasive Breast Cancer
A common way to talk about breast cancer is to classify where it started and whether it has spread. Most breast cancers begin in either the milk ducts or the milk-producing glands (lobules) of the breast. If the cancer is limited to these locations, it’s called non-invasive breast cancer. If it has spread into surrounding breast tissue, it’s called invasive breast cancer.
Ductal Carcinoma In Situ (DCIS)
When cancer begins in the milk ducts but hasn’t yet grown into surrounding breast tissue, it’s called ductal carcinoma in situ (DCIS). This is the most common type of non-invasive breast cancer. Also called stage 0 breast cancer, DCIS is an early form that is very curable.
Invasive Breast Cancer
When cancer cells originating in the milk ducts or lobules spread to surrounding breast tissue, it’s called invasive breast cancer. This type is then further classified by what’s called its receptor subtype — whether hormone receptors, such as estrogen receptor (ER) or progesterone receptor (PR), or human epidermal growth factor receptor 2 (HER2), are present on the surface of cancer cells. Knowing this information helps identify which treatments can be used with surgery to help kill the cancer.
The most common receptor subcategory of invasive breast cancer is ER-positive, HER2-negative (ER+/HER2-). This means the cancer cells contain estrogen receptors on the surface, but not HER2 receptors. Because these cancers contain estrogen receptors, they can be treated with anti-estrogen therapy — which works to kill the cancer by blocking or starving it of this hormone.
Another important group is the HER2-positive (HER2+) invasive breast cancers. Since these cells contain HER2 on the surface, treatment includes therapies designed to specifically target this receptor, called HER2 inhibitors.
Triple-Negative Breast Cancer
Most breast cancers have some combination of estrogen receptor, progesterone receptor and HER2 on the cell surface, but not all. About 15% are termed triple-negative breast cancers — meaning none of these receptors are present.Though less common, triple-negative breast cancer is an aggressive, invasive breast cancer. Though these cells lack the traditional targets, effective treatments exist for this type of breast cancer.Inflammatory Breast Cancer
Accounting for less than 5% of all breast cancers, inflammatory breast cancer is a less common type of invasive breast cancer. However, it’s aggressive — meaning it can grow and spread quickly.
It also differs from the other types of breast cancer in significant ways, including its signs and symptoms. Rather than causing a breast lump, inflammatory breast cancer is characterized by swelling and redness on the skin of the breast.
Male Breast Cancer
Breast cancer is often thought of as a disease that occurs in women, but everyone has breast tissue — and cancer can develop in the breast tissue of men, too. Male breast cancer is less common and typically occurs in older men.
As is the case for women, many different types of breast cancer can occur in men. The receptor subtype of cancer cells (HER2-positive, hormone receptor-positive or triple-negative) can vary and matters as well, but stage-for-stage has the same prognosis as for women.
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 is also called stage IV breast cancer.
Similar to chronic conditions, such as diabetes or high blood pressure, metastatic breast cancer is treatable — though it is not curable. Depending on its receptor subtype, many new treatments are available to manage metastatic breast cancer and help people live with fewer symptoms for longer.
Other Types of Breast Cancer
As mentioned, breast cancer is complex — with many different ways for it to form and grow.
Other rarer types of breast cancer include:
- Paget disease of the breast – starts in the milk ducts and spreads to the skin of the nipple
- Angiosarcoma – typically occurring in a previously radiated breast, this type of breast cancer starts in the skin
- Phyllodes tumor – usually benign though occasionally cancerous, these tumors start in the connective tissue of the breast
- Lobular cancer in situ (LCIS) – although not technically a type of breast cancer, abnormal cells in the lobules of the breast is a high-risk marker for the development of breast cancer