Types of Breast Cancer
- Ductal Carcinoma In-situ (DCIS): The earliest stage of ductal cancer, this is a non-invasive process. This means it is unlikely to spread beyond the breast. When we look at this cancer under the microscope, we see cancer cells trapped within the duct but not invading into the nearby tissue. When found at this stage, proper treatment results in a 99% survival. Chemotherapy is not needed for this type of cancer so there is a huge benefit to find disease at this stage. Fortunately, DCIS often develops calcium deposits early in its development and this process shows up as "suspicious microcalcifications" on a screening mammogram. A stereotactic needle biopsy of these microcalcifications is then performed to make the diagnosis.
New Ways of Thinking about Types of Breast Cancer
- Invasive Carcinoma:
- Infiltrating Ductal Carcinoma: The most common type of breast cancer is called infiltrating ductal carcinoma. This type of cancer starts in the milk duct, then invades the local breast tissue. The body often responds to this type of cancer by producing a “scar” around it which makes the tumor feel firm on exam, and it will be visible as a white spot on your mammogram.
- Infiltrating Lobular Carcinoma: The second most common type of breast cancer is called infiltrating lobular carcinoma. It starts in the breast lobules and grows in a sneaky, infiltrating pattern that may be difficult to feel on exam or see on the mammogram. Once diagnosed, it is treated the same as ductal carcinoma, but because of its poorly contained growth pattern, it may require extra imaging such as breast MRI to define the amount of the disease in the breast.
- There are numerous other forms of Invasive Carcinoma such as papillary, mucinous, tubular, and so forth which are often treated in the same way as infiltrating ductal carcinoma.
Often breast cancer types are categorized by what they look like under a microscope, but it is more useful to think of breast cancer types by the things that they use to grow. If we can understand what makes a cancer grow, we can make it stop growing, which is the goal of all cancer treatments. We can tell what a cancer cell is using to grow by what "receptors" it has on its cell surface.
Hormone Receptor Positive
When a cancer cell has estrogen or progesterone receptors on its surface, it is using a woman's own natural estrogen to grow. In this case, blocking the estrogen receptor, or making estrogen unavailable to the cancer cell is effective therapy to stop cancer growth. Often, these "hormone receptor positive" cancers (also known as "ER/PR" positive) are so responsive to hormone blocking approaches that chemotherapy is not needed to control their growth. Genomic testing is often used to determine if patients with these types of breast cancer will benefit from chemotherapy or not.
However, if the cancer cell does not have these hormone receptors on its surface, it is called "hormone receptor negative" or "estrogen receptor (ER) negative." These cancers will not respond to hormone blocking strategies and commonly need chemotherapy treatment control their growth.
The "Her-2-neu" receptor is another receptor that is important to a cancer cells growth. Only about 20% of all breast cancers have this receptor and when it is present, the cancer can grow more rapidly. Luckily, a drug called Herceptin, is specifically designed to block this receptor and is very effective in controlling the growth of these "Her-2 positive" breast cancers. Because of its aggressive nature, this type of cancer is always treated with chemotherapy along with Herceptin.
Triple Negative Breast Cancer
When a cancer cell has neither the hormone receptors nor the Her-2-neu receptor, it is called "ER/PR/Her-2 negative" or "triple negative" breast cancer. There is not a lot of understanding on how these cancers grow, but they do not respond to either hormone blocking drugs or to Herceptin. They are always treated with chemotherapy and they are a bit more difficult to control, so treatment tends to be more aggressive.