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How Mohs Surgery Is Changing the Way Skin Cancer Is Treated

Years ago, if a patient needed surgery for skin cancer, that meant a trip to the hospital and an overnight stay. But today, a procedure called Mohs surgery can be done in the convenient setting of a doctor’s office, and the patient goes home the same day.

Mohs is a very specialized procedure; there are only 12 fellowship-trained Mohs surgeons in the greater Raleigh-Durham-Chapel Hill area, two of them with UNC Health Care.

Raj Varma, MD, of the UNC Dermatology and Skin Cancer Center answers some of the most common questions that referring physicians have about Mohs surgery.

What is Mohs surgery?

Mohs micrographic surgery is a surgical technique and process where a tumor is removed and meticulously evaluated under the microscope to ensure all the cancerous cells are removed. Technically, it is an excision of cancerous tissue with subsequent complete circumferential and deep margin assessment. (This is in comparison to “standard,” or non-Mohs, excisions where only a sampling of the margins are evaluated.) Many people think of the process as taking layers of skin and checking each layer until all the cancer is removed. However, this is somewhat misleading because many skin cancers can invade deeper into the skin, so the “first layer” or “first stage” of the surgery might actually remove several layers of skin to get a clear margin. Frederic Mohs, MD, at the University of Wisconsin developed this technique.

What type of cancer is Mohs surgery used to treat?

Mohs surgery is considered the gold standard surgical treatment for skin cancer. For the most common types of skin cancer—basal cell carcinoma and squamous cell carcinoma—studies show Mohs surgery has a 98 to 99 percent cure rate. Some Mohs surgeons also treat melanoma, although it’s only offered at a few places in North Carolina, including at UNC Medical Center with Brad Merritt, MD. Mohs surgery can also be used to treat extramammary Paget’s disease (a cancer characterized by a chronic rash in the genital area), dermatofibrosarcoma protuberans (a slow-growing and often unrecognized tumor that can have the appearance of a thick, irregular scar), and other rare skin cancers.

Are there times when the Mohs procedure isn’t the best method for treating skin cancer?

Yes. The surgery is limited by being an outpatient procedure, so if the tumor extends to bone or into another vital structure that cannot be excised in our office, then we will stop the Mohs procedure and obtain assistance from our colleagues in other surgical specialties or radiation oncology. Also, there are times when tumors have already spread to nerves, lymph nodes or other organs, in which case we would defer treatment plans to another specialty, such as surgery or medical or radiation oncology.

What kind of training does a Mohs surgeon receive?

Here at UNC Medical Center, Dr. Merritt and I are both members of the American College of Mohs Surgery (ACMS), which was founded by Dr. Frederic Mohs. The ACMS requires its members to complete an extensive one- to two-year fellowship training program in Mohs surgery, pathology and reconstructive surgery after they have completed dermatology residency training. During their ACMS fellowships, physicians participate in at least 500 Mohs surgery cases under the supervision of an experienced Mohs surgeon. Many have performed or assisted in more than 1,000 surgeries.

On the other hand, almost all dermatologists learn the Mohs surgery procedure while in their residency training. Some go on to perform Mohs surgery without additional formal training after residency. Mohs surgeons who have not completed a fellowship are listed as members of the American Society for Mohs Surgery (ASMS).

This difference between the ACMS and the ASMS—and between fellowship-trained Mohs surgeons and those who have not been fellowship-trained—is an important distinction. To date, there are fewer than 60 fellowship-trained Mohs surgeons in North Carolina.

How can I refer my patients to UNC Medical Center for Mohs surgery?

You can refer patients with basal and squamous cell carcinomas, as well as a variety of other cutaneous malignancies, after the diagnosis has been confirmed by biopsy. We also accept referrals for some melanoma cases. Call our UNC Dermatology and Skin Cancer Center office at (984) 974-3685 to make a referral.


Learn more about the UNC Mohs Clinic or call (984) 974-3685 to refer a patient.

Raj Varma, MD, specializes in Mohs surgery at UNC Dermatology and Skin Cancer Center at Southern Village. He is a member of the American College of Mohs Surgery and an assistant professor at the UNC School of Medicine.