Today, with our better understanding of breast cancer cells, we can take an individualized approach to treating breast cancer based on tumor biology. Tumor biology refers to characteristics of the cancer cells. These characteristics describe the type of cancer cells, how aggressive the cells appear under the microscope, and how we expect the cancer to respond to treatment.
Two characteristics – the “Histological Grade” and the “Receptor Status” – are used to determine which treatment path to offer each woman based on her unique breast cancer.
• Histological Grade
– This describes the aggressiveness of the cells. Grade 1 is low grade, meaning the cells divide and grow slowly, and look like each other. These cells could be labeled as “better behaved.”
Grade 2 are “in between,” cells that are not the best behaved, but not the worst behaved either.
Grade 3 is high grade. These cells look very different from each other. They divide and grow rapidly. These are more dangerous cells.
• Receptor Status
– Receptors on any cell are like a lock to a door. Particles, molecules, substances in the blood are ingredients that act like a key to fit the lock. If you have the right key, the door opens and the ingredient can enter the cell and be used for making new cells. Testing for receptor status on cancer cells helps to understand the behavior of the cells and how they will respond to different medications.
For breast cancer, there are three main categories of cancer cells based on receptor status:
• Estrogen Receptor (ER) and Progesterone Receptor (PR)
– About 60 percent of breast cancer cells use the hormones estrogen and progesterone to make new cancer cells. Having positive ER and PR receptors identifies the cancer as using these hormones to grow.
– This is also a receptor specific to breast cancer cells. Having your cancer cells either positive or negative for HER2 receptors significantly affects your breast cancer treatment plan.
• Triple Negative
– This refers to cancer cells that have no receptors on their cells. There are no estrogen, progesterone or HER2 receptors present.