When a breast tumor is removed, either by biopsy, lumpectomy, resection, or mastectomy, some of the surrounding breast tissue is also removed. The pathologist places the excised tissue in a special ink and examines the tissue under the microscope. The outermost edge of the tissue is examined. Then, the pathologist checks the edges of the tumor tissue to see whether or not they contain cancer cells, and how far from the edge the cancer cells are. This study allows the pathologist to determine whether or not all of the tumor was removed.
Doctors use the term margin or margins of resection to refer to the distance between the breast tumor and the edge of the tissue. The margins are measured on all six sides: front and back, top and bottom, left and right. Knowing how close the cancer cells are to the edge of the tissue will help your doctor decide upon the next step in your treatment, i.e.: additional surgery, radiation, etc.
A breast tumor’s margins are labeled in one of three ways depending on the pathologist’s findings:
Positive Margins, which mean that there are cancer cells beyond the edge of the tissue.
Negative Margins, which mean that no cancer cells have been found in the area beyond the edge of the tumor. A negative margin is one of the terms that is slightly ambiguous, perceived differently by different pathologists. Some pathologists label a tumor’s margin “negative” if even one normal cell is found between the cancer cells and the edge of the tissue. Other pathologists believe that there most be at least 2 millimeters between the cancer cells and the edge of the tissue for a margin to be labeled “negative.”
Close Margins, which means that the tumor’s margins are neither negative nor positive, but somewhere in-between a negative and positive classification.
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