Lumpectomy margins are the rim of normal tissue surrounding the cancer tumor that is often removed with the tumor during the surgery to ensure the cancer is completely gone. After the procedure, a pathologist examines the removed tissue to check for remaining cancer cells in the lumpectomy margins. Margins free of cancer are considered clean, clear or negative, which is the goal of the surgery. Margins that still have cancer cells are positive and more surgery, or re-excision, may be necessary to remove them.
Checking the margins is typically done during the lumpectomy, but analyzing the margins can take about a week, according to Breastcancer.org. Margins also are checked after surgical biopsy and mastectomy.
A new standard published recently in the Journal of Clinical Oncology suggests that a 2-millimeter clean margin offers enough protections against the recurrence of ductal carcinoma in situ (DCIS) for women treated with lumpectomy and whole-breast radiation. DCIS is the earliest form of cancer or stage 0 cancer.
The guidelines were issued because of disagreement about how big clean margins should be. About 1 in 3 women treated for DCIS has to have more surgery because doctors decide the margins should be bigger, Breastcancer.org reports. Some doctors want 2 mm or more of normal tissue removed and others consider a 1-mm rim of health tissue or less to be enough of a clean margin.
Clean lumpectomy margins mean that no cancer cells can be seen in the outer edge of the removed tissue. The pathology report may also say how wide the clear margin is along with the distance between the outer edge of the surrounding tissue removed and the edge of the cancer. No additional surgery is usually needed.
A positive lumpectomy margin means cancer cells come to the edge of the removed tissue. More surgery is usually needed to remove any remaining cancer.