Resection margins are the area around a section of tissue removed during surgery to treat a tumor. They may include completely healthy, normal cells, or a mixture of healthy and cancerous tissue. In some cases, a surgeon fails to cut out all the cancer, and the margins are cancerous. The goal of cancer surgery is usually to get “clean margins,” meaning that a pathologist cannot identify any cancer cells on the margins of the sample.
In planning for surgery to remove a tumor, the surgeon will use medical imaging and other tools to determine the location, extent, and size of the growth. Once the surgeon is inside the patient, the cancerous tissue is usually visibly different, providing further guidance. Surgeons usually try to cut out the tissue in a single incision, to prevent situations where they cut into cancer cells, breaking them up and allowing them to disperse into the body. The surgeon will send the removed tissue to a lab for analysis by a pathologist.
Pathologists start by inking tissue samples so they will be able to easily identify the edges as they cut the sample up. The pathologist will examine the resection margins to determine whether they are positive, negative, or close. Positive margins are those where cancer cells are present. In negative margins, the tumor is entirely encapsulated in healthy tissue. Close margins fall between these two extremes, as for example when cancer cells are near the edges, but not at the absolute margin.
Information about the resection margins is important for planning additional cancer treatment. When a tumor is hard to identify, the doctor may request a biopsy while she is still in the operating room, to determine if she needs to cut more tissue away to get clean margins. Otherwise, the surgeon and oncologist will meet to discuss the resection margins after surgery and determine what kinds of chemotherapy, radiation, and other treatments would be most appropriate for the patient's case.
Patients can ask about their resection margins if they are curious and want to take a more active role in cancer care. Their physicians can explain the biopsy results and discuss what they mean. Some cancers grow slowly, and close margins may not be a cause for concern in those cases, while with others, close or positive margins are a serious cause for concern, as they indicate an increased chance of recurrence even with radiation or chemotherapy to attack the cancer.