By Delthia Ricks

Few issues involving breast-conservation surgery are more important than how much of the healthy-appearing tissue surrounding a tumor should be removed during surgery. This band of tissue, known as the margin, is what pathologists examine to ensure that the cancer hasn't migrated from the tumor into healthy cells.

When the rim of tissue is cancer free, then the margins are considered to be clear or clean. But if the pathologist identifies even a few tumor cells, the margins are considered positive for cancer. It takes only a single cancer cell to start another tumor, so removing or killing all of them is central to successful cancer treatment. That's why if the margin is positive, the surgeon will operate again to remove tissue around the former tumor bed—and a pathologist will again run tests for positive or negative margins. Sometimes there are several surgeries before the margins test clear.

Surprisingly, despite the importance of removing all vestiges of cancer, there is no consensus on how much of the tissue surrounding the tumor a surgeon should remove initially. Some centers take only a 2- or 4-millimeter rim of tissue with the tumor; others take as much as 10 or more millimeters. The amount removed usually depends on the size of the tumor, its location and the standard in force at the medical facility where the surgery is performed. For example, surgeons at the University of Michigan's breast care center generally remove a 3-millimeter rim of healthy tissue along with the tumor. But at nearby William Beaumont Hospital in Royal Oak Michigan, the standard generally is a 2-millimeter border.

A number of breast cancer specialists are concerned by the absence of a standard for margins. They cite high rates of re-excision (additional surgery) as a sign that a wide enough margin is not being removed initially. Rates of re-excision, some studies suggest, are nearly 50 percent, even at many of the nation's top cancer centers. In addition to leaving a patient vulnerable to a local recurrence, additional surgeries subject her to the unavoidable risks of anesthesia and surgical procedures.

Unfortunately, wide margins can defeat the reason for having a lumpectomy in the first place. "When you excise more than 10 millimeters, your chances of local recurrences are smaller, but it distorts the breasts," explains Merav Ben-David, M.D., a medical and radiation oncologist at the University of Michigan Medical Center in Ann Arbor. "The shape is worse and the cosmetic results can be horrible."

Of course, factors such as the type of cancer a woman has and the cancer's degree of aggressiveness influence how much tissue a surgeon initially takes. But recent studies have shown that no matter the kind of breast cancer, obtaining clean margins the first time protects against having the cancer return locally.

Ben-David's own study examined outcomes in women with DCIS (ductal carcinoma in situ, which means that the cancer is contained within the milk ducts) who had been treated with breast conserving surgery and radiation therapy. "In our study," Ben-David says, "the women who had margins less than 3 millimeters wide, experienced more local recurrences than women who had wider margins."

The Imaging Problem

Part of the difficulty in achieving clean margins may be remedied by better imaging technology. Breast cancer surgeon Deanna Attai, M.D., in Glendale, California, uses a handheld ultrasound device to help determine margins. "There is no perfect method to accurately predict margins, but ultrasound has allowed me to better predict or identify exactly where the lesion is, how deep or close it is to the skin, etc., which helps me to better plan how much tissue to remove."

Research also is under way to improve imaging of the tumor and the surrounding tissue at the time of surgery, which should help lower rates of re-excision. A promising new scanning technology includes the use of terahertz light rays (a wavelength in the electromagnetic spectrum that can be used to quickly scan margin samples). At a meeting of the American Society of Breast Surgeons in April, researchers reported on the results of a handheld device that used terahertz technology. They tested the scanner during the surgeries of 41 patients. After the surgeon removed margin tissue, the researchers scanned each sample on the spot to see if they could identify cancerous cells. The terahertz device correctly identified cancer cells in 9 out of 12 margin samples. According to the study's principal investigator Lorraine Tafra, M.D., director of the Breast Center at Anne Arundel Medical Center in Annapolis, MD., "This device has the potential to decrease the need for re-excisions and significantly contribute to improving the accuracy of breast-conserving surgery."

Until then, women may want to discuss the issue with their surgeons. How wide a margin do they plan to remove? And what will that mean for the cosmetic look of your breast and the likelihood of recurrence? Armed with this knowledge, you'll have a better sense of what to expect immediately after surgery and further down the road.