The surgeon’s goal during surgery is to take out all of the breast cancer along with a rim of normal tissue around it. This is to be sure that all of the cancer has been removed.
During or after surgery, a pathologist examines this rim of tissue — called the surgical margin or margin of resection — to be sure it’s clear of any cancer cells. If cancer cells are present, this will influence decisions about treatments such as additional surgery and radiation. Margins are checked after surgical biopsy, lumpectomy, and mastectomy.
Your pathology report may say that the surgical margins are:
- Clear (also called Negative or Clean): No cancer cells are seen at the outer edge of the tissue that was removed (the tumor along with the rim of surrounding tissue). Sometimes the pathology report also will tell you how wide the clear margin is — the distance between the outer edge of the surrounding tissue removed and the edge of the cancer. When margins are clear, usually no additional surgery is needed.
- Positive: Cancer cells come right out to the edge of the removed tissue. More surgery is usually needed to remove any remaining cancer cells.
- Close: Cancer cells are close to the edge of the tissue, but not right at the edge. More surgery may be needed.
An important note: There is not a standard definition of how wide a “clear margin” has to be. In some hospitals, doctors want 2 millimeters (mm) or more of normal tissue between the edge of the cancer and the outer edge of the removed tissue. In other hospitals, though, doctors consider a 1-mm rim of healthy tissue — and sometimes even smaller than that — to be a clear margin. As you talk with your doctor about whether your margins were clear, positive, or close, you also can ask how “clear” is defined by your medical team.