Additional tests will be done on the tumor tissue to gather more information about how the cancer is likely to behave and what treatments will be most effective. Examples include:
Grade: A pathologist examines the cancer cells under a microscope and determines how abnormal they appear and behave when compared with healthy breast cells. The lower the grade, the more closely the cancer cells resemble normal cells, the more slowly they grow, and the less likely they are to spread. There are three grades of invasive ductal carcinoma: low or grade 1; moderate or grade 2; and high or grade 3.
Grade 1 invasive ductal carcinoma cells, which are sometimes called “well differentiated,” look and act somewhat like healthy breast cells. Grade 3 cells, also called “poorly differentiated,” are more abnormal in their behavior and appearance.
Surgical margins: When cancer cells are removed from the breast, the surgeon tries to take out the whole cancer with an extra area or “margin” of normal tissue around it. This is to be sure that all of the cancer is removed. The tissue around the very edge of what was removed is called the margin of resection. It is looked at very carefully to see if it is clear of cancer cells.
The pathologist also measures the distance between the cancer cells and the outer edge of the tissue. Margins around a cancer are described in three ways:
- Negative: No cancer cells can be seen at the outer edge. Usually, no more surgery is needed.
- Positive: Cancer cells come right out to the edge of the tissue. More surgery may be needed.
- Close: Cancer cells are close to the edge of the tissue, but not right at the edge. More surgery may be needed.
- Hormone receptor assay: This tissue test determines whether or not the breast cancer has receptors for the hormones estrogen and progesterone. A positive result means that estrogen or progesterone (or both) has the ability to fuel the cancer cells’ growth. If the cancer is hormone-receptor-positive, your doctor likely will recommend hormonal therapies that block the effects of estrogen or lower estrogen levels in the body. Examples include tamoxifen and aromatase inhibitors. If you are premenopausal, your doctor may discuss other options, such as using medications to shut down your ovaries temporarily, or even surgically removing them. The ovaries are the body’s main source of estrogen before menopause.
HER2-receptor status: Other tests are done to find out whether the breast cancer cells make too many copies of (overexpress) a particular gene known as HER2. The HER2 gene makes a protein known as a HER2 receptor. HER2 receptors are like ears, or antennae, on the surface of all cells. These HER2 receptors receive signals that stimulate the cell to grow and multiply. But breast cancer cells with too many HER2 receptors can pick up too many growth signals. This causes them to start growing and multiplying too much and too fast. Breast cancer cells that overexpress the HER2 gene are said to be HER2-positive. Treatments called HER2 inhibitors work against HER2-positive breast cancers by blocking the ability of the cancer cells to receive growth signals. HER2 inhibitor medicines include Herceptin (trastuzumab), Kadcyla (chemical name: T-DM1 or ado-trastuzumab), Nerlynx (chemical name: neratinib), Perjeta (chemical name: pertuzumab), and Tykerb (chemical name: lapatinib).
HER2-positive cancers also can be treated with Tykerb (chemical name: lapatinib), a medication that interferes with the activity of HER2 from inside the cell. Tykerb limits the amount of energy the breast cancer cells have to grow and multiply.
These tests are done on the tissue that is removed during biopsy, or, in the case of surgical margins, after the surgery to remove the cancer.
For more information about these tests and other tests and what their results mean, visit the Your Diagnosis section.