Breast cancer is an umbrella term that describes 15 different types of cancerous tumors in the breast.
Cancers are first classified according to where they begin in the breast-either in the duct or lobule. The term breast cancer refers to cancer that develops in the cells that line either duct or lobule.
Cancers are then classified as being in situ or invasive (infiltrating). In situ means the cancer is still inside the walls of where it began. Invasive means the caner has grown through the walls of where it began.
Ductal carcinoma in situ or DCIS accounts for roughly 15-20% of new breast cancer diagnoses each year. It is considered non-invasive breast cancer, which means that it does not have the ability to spread to the lymph nodes under the arm or other parts of the body. The standard treatment options are directed at the breast and may include surgery, radiation and or hormone blockade medication.
Invasive Breast cancer has spread into surrounding breast tissue. The most common types are invasive ductal carcinoma and invasive lobular carcinoma. Invasive ductal carcinoma makes up about 70-80% of all breast cancers.
Breast cancer cells taken out during a biopsy or surgery will be tested to see if they have certain proteins that are estrogen or progesterone receptors. When the hormones estrogen and progesterone attach to these receptors, they fuel the cancer growth. Cancers are called hormone receptor positive or hormone receptor negative based on whether or not they have these receptors (proteins). Knowing the hormone receptor status is important in deciding treatment options. If the cancer cells don’t have hormone receptors, they are called hormone receptor negative.
Her2 is a growth promoting protein on the outside of all breast cells. Breast cancer cells with higher than normal levels of Her2 are called Her2 positive.
Grade is what a cancer cell looks like under the microscope. Grade 1 is well differentiated and like a normal cell. Grade 2 is moderately differentiated, and Grade 3 is poorly differentiated and can grow faster.
The staging system most often used for breast cancer in the American Joint Committee on Cancer (AJCC) TNM system.
Before surgery, the cancer will be given a clinical stage– this is usually the results of physical exam, biopsy and imaging tests. The clinical stage is used to help plan treatment.
Pathologic stage (also called the surgical stage) is determined by examining tissue removed during an operation.
In both staging systems, 7 key pieces of information are used to come up with the breast cancer stage:
- Size of the tumor (T)
- Spread to nearby lymph nodes (N)
- Spread (metastasis) to distant sites (M)
- Estrogen Receptor status (ER) (hormone receptor on breast cancer cell)
- Progesterone status (PR) (hormone receptor on breast cancer cell)
- Her 2 status (Her 2) (protein on the breast cancer cell)
- Grade of the cancer (G)