What Is a Surgical Margin?

A surgical margin is the edge of a growth removed from a patient. The growth is examined by a pathologist who determines whether the surgeon successfully removed all of the cancerous cells. In a report, the pathologist may describe the margins as positive, close, or negative in a reference to how close the cancer cells are to the edges. Prognosis tends to improve with negative margins, and can be less rosy for a patient with a positive or close surgical margin.

If the pathologist describes the surgical margin as positive, it means that cancer cells were found right along the edge. The surgeon, rather than taking out the whole growth, cut through the cancer and only got part of it. Remaining cells inside the body can continue to grow and colonize the area. Treatment with chemotherapy and radiation, along with potential follow up surgeries, may work to suppress the cancer growth and allow the patient to recover.

Sometimes positive surgical margins are unavoidable. A cancer may be in a delicate location that makes it hard for the surgeon to get it all; in this case, the goal is de-bulking, rather than complete incision. The surgeon wants to cut out as much of the growth as possible to improve the chances of a positive outcome. Other cases can create clouded margins because the surgeon took the growth out in chunks, making it hard to offer a definitive diagnosis.

Close, also known as narrow, surgical margins occur where cancer cells are near the edge, but not actually touching it. There is a chance there may be some left in the body, which means the surgery is not as successful as hoped. Prognosis can still be good, depending on the type of tumor, and the pathologist may have some notes on this subject, based on experience with similar tumors and patients. In prostate cancer, for example, sometimes a narrow surgical margin is perfectly acceptable.

Negative or wide margins are the ideal outcome. This pathology finding represents a nice strip of healthy tissue all the way around the tumor, indicating that the surgeon removed it in a complete capsule. The probability of leaving cancer cells behind is extremely small, and the wide margins mean that the surgeon probably didn’t break up the tumor and accidentally seed the site with malignant cells. Also known as a clear surgical margin, this is typically associated with a better prognosis for the patient, especially with accompanying treatment to provide complete care.