January 2020

“Mohs, which stresses taking thin margins, has no place in treating invasive melanoma.”

It is a classic case of a hammer in search of a nail. Slow Mohs surgery for melanoma not only makes no sense, it is a bad idea that compromises treatment of this potentially deadly cancer.

While Mohs surgery still carries the name of its originator, Dr. Frederic Mohs, the technique has evolved from the 1930’s. Even so, the basic premise is the same. Now called Mohs Micrographic Surgery it is still the exclusive purview of Dermatology. The goal of Mohs is to remove skin cancers with clear margins and as little normal skin as possible. It is always done in an office setting. The skin cancer is removed under straight local anesthesia, the patient bandaged and sent out to a waiting room, and the surgeon examines the specimen to assess the margins. If they are clear, the patient returns to the surgery suite to have the site sutured or otherwise closed in some fashion. If the margins are not clear, the patient is brought back, more skin removed, and the process repeats until clear margins are obtained. Each excision stage takes around 45 minutes or so. With Mohs, the average skin cancer requires 1.7 excisions, which means that many require two or more excisions for clear margins.

Until fairly recently, Mohs was confined to non-melanoma skin cancers such as basal cell and squamous cell. These are typically confined to a small area of skin and are only extremely rarely life-threatening. While Mohs has a place in the treatment of skin cancer, I believe that it is sometimes used in situations where it is not the best option.

Recently, dermatologists have begun to perform something called “slow Mohs” for early melanoma cancer. Invasive melanoma cancer, even an early one, is a potentially life threatening condition. Excision is the primary treatment and wide excision, i.e. taking a wide margin of skin around the cancer, is the sine qua non of melanoma treatment.  There is no place for taking close margins, even for the earliest, non-invasive melanoma, melanoma in situ. Mohs, which stresses taking thin margins, has no place in treating invasive melanoma. Even with very early, non-invasive melanoma in situ, the accepted standard is wide margins of no less than 5 mm.

The term “slow” Mohs reflects the fact that the process always takes more than one day. Processing a melanoma specimen takes 1-2 days. Therefore, the patient is sent home with their open wound bandaged and made to return a few days or up to a week later for either closure or yet another excision. One patient referred to me underwent three excisions over the course of three weeks! This is painful and distressing to patients and increases the risk of infection. There is no excuse for this. This is not the case with traditional wide excision.

I spoke to a dermatopathologist who processes a lot of slow Mohs specimens. She is not a fan of the procedure because of the way the specimen is taken and has to be processed. This makes it difficult, if not impossible, to establish the final margin, which is the closest the melanoma comes to the final surgical margin. Let me stress this: the goal of melanoma cancer excision is not to remove it with the smallest possible margin, which is the goal of slow Mohs. It is to remove the cancer with a generous margin, usually deemed to be 5 mm or more. Most slow Mohs excisions take only a 1-2 mm margin. This small difference can be the difference between curing the cancer and experiencing a recurrence, or worse.

Why the recent push for Mohs in treating a life threatening cancer? I believe that Mohs for melanoma reflects a misguided ordering of priorities. The first priority in treating melanoma is to cure the patient. The concern over reconstruction and the cosmetic result are important, but clearly secondary to that critical primary goal. In 1957 Drs. Harold Gillies and D. Ralph Millard, Jr., two of the pre-eminent plastic surgeons of the last century, wrote, “Too often, the general surgeon will ask courteously whether sparing such and such a bit will make the repair easier. He is genuinely trying to help in the repair and forgetting his primary duty. The answer must be, “I couldn’t care less. You remove the malignancy so it does not recur, whatever the deformity, and let me worry about the repair”.

Slow Mohs attempts to force a deadly cancer into the same treatment category as non-melanoma skin cancers, which are not life threatening. Ask any general or plastic surgeon what they think about slow Mohs and you will hear almost universal condemnation of the procedure. Even among dermatologists, slow Mohs is controversial. The bottom line is that it simply makes no sense. I would never allow myself or anyone I know to be treated for any melanoma using slow Mohs.

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