Skin Cancer and the Mohs Surgery Technique

HumAdminDermatology & Skin Cancer Center, Health and Healing, Mohs Surgery, Southern Dermatology News & Articles

Dr. Wilmoth H&H-MohsThe incidence of skin cancer has been on the rise since the 1990s,” says Dr. Gregory Wilmoth of Southern Dermatology and Skin Cancer Center in Raleigh. “Now in 2016, the incidence of skin cancer is the highest it’s ever been.” Dr. Wilmoth, who completed his dermatology training in Minnesota before beginning his practice as a dermatologist in Florida, says he believes there are a number of reasons for the increased rates of skin cancer he is seeing today.

“There are several factors,” he says. “The demographics of the Baby Boom population are such that health care in general is more in demand than it has been in the past, as the majority of that population is crossing age 65. More skin cancers occur in the elderly than in younger groups. In addition, I think the social norm of looking tan is still part of the problem—people get more intentional sun exposure today than they did generations ago.”

And there is another culprit suspected by Dr. Wilmoth that may strike some as counter intuitive. Sunscreen may actually be part of the problem, he notes. “When people are exposed to sunlight,” he explains, “even when they don’t get burned, sun damage, and therefore stimulation for skin cancers, can still occur.

“Sunscreen,” he says, “blocks ultraviolet A light, which is the light that causes sunburns. However it does not block ultraviolet B light. DNA can be damaged by any ultraviolet light regardless of whether you get a sunburn. So because of sunscreen, people are now able to do something they were never able to do before: go out on the beach and soak up eight hours of ultraviolet light and not get a sunburn. And without a burn, they feel safe from the effects of excessive exposure.”

In this sense, he suggests, you could actually think of a sunburn as a protection mechanism—like the body’s own alarm system letting you know it’s time to get out of the sun. “My message to patients is always that sunscreen is part of what you need to be doing, but it isn’t all. It doesn’t provide complete protection. Clothing, staying in the shade, and being careful about what time of day you are out in the sun are much more protective measures to take in addition to wearing appropriate sunscreen.”

Mohs Surgery—a Challenging Procedure

Since his early days as a dermatologist in Florida, Dr. Wilmoth has been perfecting the art of Mohs Surgery, a micrographic surgical method developed by Dr. Frederic E. Mohs in the 1930s.

“We use Mohs surgery predominately for non-melanoma skin cancers on the head and neck,” Dr. Wilmoth says, “because in those areas, there are two things that happen with skin cancers: One is that you don’t have the luxury of a lot of extra skin available to repair the area later, so we want to be able to remove the cancer with the smallest margin of normal skin as possible. Mohs surgery allows us to do that. The other reason we use Mohs is for recurrent or large tumors.”

Fifteen years ago, when Dr. Wilmoth came to the Triangle, he was one of only three doctors in the area performing Mohs surgeries. “The problem with traditional margin techniques of skin cancer removal is if you want to remove a basal cell carcinoma, for instance, with a 95 percent cure rate, you’re going to have to cut 4mm all the way around it. That can turn into a fairly large area very quickly if you’re taking it out of an eyelid or the side of the nose.

“With Mohs surgery,” he explains, “I can remove the cancer and only take a 1 mm margin around it, then check 100 percent of that margin to make sure I got it all. Once I get it under the microscope, if any part of the margin is positive for cancer cells, I can see exactly where I may need to go back and take a little more out without cutting around the whole area again. In this way, the Mohs technique spares skin, which is of great importance when we’re talking about the face and neck.”

Another issue with traditional margin techniques, Dr. Wilmoth explains, is that, in addition to cutting a relatively large margin around the cancer, it only provides a crosssectional look at the sample. This only allows a practitioner to see around two percent of the margin. So, if the cancer has grown out into the skin in any of the other 98 percent of area that isn’t shown by that cross-sectional piece, it will be missed.

“Mohs surgery offers the highest cure rates of any skin cancer removal technique we have,” he says, “because it allows us to check 100 percent of the margin, and to keep checking 100 percent of any new margins that are taken, if necessary.”

As Dr. Wilmoth explains, “You remove the cancer with a very thin margin—of about 1mm. Then you process that tissue by placing it in something called a cryostat, which is a very cold refrigerator—minus 20 degrees Celsius. In the cryostat we have a microtome, which allows us to cut the tissue in a precise way. The tissue is sliced into seven micron thick slices, and placed on microscope slides where it can be stained. This allows us to see the details of the cells under the microscope, and to see 100 percent of the margin—the difference between the cancerous and noncancerous cells.”

These slices also function as a map, showing Dr. Wilmoth where there are still cancerous cells left—if any. “If I see nothing but healthy skin all the way around, we know we have got it all,” he says. “If I look and see skin cancer anywhere on the slide, I know I missed some because I’ve cut through it. Then, I can mark it and know where to go back and take out a little more.”


The other part of this process that can pose a challenge is reconstruction of the area after the skin cancer removal. “We do a lot of reconstructive work,” Dr. Wilmoth says. “In the last 20 years, dermatologists have become the specialists who most often take care of skin cancers. And, where it used to be that a plastic surgeon would do the reconstruction once the cancer was removed, now it’s mostly dermatologists doing that, as well.

“Sometimes I’ll do skin flaps,” Dr. Wilmoth continues, “and this is another place that Mohs surgery offers an advantage over other techniques. By keeping those margins as small as possible, and removing as little skin as we can, especially in facial areas, it leaves us with a much smaller area to reconstruct—which ultimately is going to provide better cosmetic results.” h&h

Originally published in Health & Healing in the Triangle, Vol. 19, No. 3, Health & Healing, Inc., Chapel Hill, NC, publishers. Reposted with permission.