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Edward W. Seger MD MS Division of Dermatology

The origins of Mohs micrographic surgery trace back to nearly a century ago in Wisconsin, where Dr. Frederic Mohs developed what was initially known as chemosurgery. In the decades since, the Mohs technique has evolved into an essential cog in our treatment of skin cancer. Dermatologists with additional training in Mohs surgery have the expertise to remove skin cancer, act as the dermatopathologist in reviewing tissue samples, and then as the reconstructive surgeon to restore functionality and optimize cosmetic outcomes. With a highly trained staff and an in-house histopathology laboratory, this comprehensive and intricate procedure allows patients to leave that day knowing their cancer has been successfully treated.

Mohs utilization continues to increase, and this growth has opened new avenues to expand our scope of practice and optimize our techniques. We are treating more melanomas with Mohs than ever before, and what was once a multi-day process requiring paraffin embedded tissue samples, can now be accomplished in a few hours with same day reconstruction. The Mart-1 stain has revolutionized how we treat melanoma, and Mohs surgery with immunohistochemistry provides superior outcomes when compared to traditional excisions. Immunohistochemistry is the use of special stains for tissue to better and more specifically highlight tumor cells. While not new, its use has grown considerably over the last decade. Alongside similar stains such as CD-34, CK7, and SOX10, we now have more specific and unique markers to help identify tumors under the microscope. This improved sensitivity in detecting and removing cancer allows us to improve long-term outcomes and expand the types of malignancies that we can treat. 

Much of the benefit associated with the Mohs procedure is related to intraoperative margin control. Mohs surgeons review 100 percent of the peripheral and deep margins to verify tumor eradication, compared to less than 1 percent of margins evaluated during traditional excisions. This level of detail allows Mohs to provide the highest cure rates for nearly all cutaneous malignancies, and its utilization is expanding into less common cancers. For example, Mohs surgeons are now treating extramammary Paget disease, sebaceous carcinoma, and microcystic adnexal carcinomas. Many adnexal and sebaceous malignancies extend far beyond clinically evident margins, increasing risk of recurrence and metastasis if they are not adequately treated. By assessing complete tumor margins, Mohs surgery reduces risk of recurrence for these tumors and spares as much normal tissue as possible in functionally and cosmetically important anatomical areas.

Beyond reduced recurrence rates, the Mohs procedure and reconstruction is performed almost entirely in an outpatient setting under local anesthesia. This allows patients to avoiding the risks associated with general anesthesia and potential hospitalizations. Numerous studies have shown that patients prefer this treatment setting, and they tolerate large and complex repairs well without sedation. Speaking of complexity: Mohs surgeons perform more than 10 times as many intermediate and complex repairs when compared to other surgical specialties while performing all forms of flap and graft reconstruction. This level of reconstruction expertise helps maximize the long-term cosmetic and functional outcomes of our patients.

The field of Mohs micrographic surgery has evolved substantially from its inception in the 1930’s and has become the gold standard treatment for virtually all high risk and aggressive skin cancers. For providers who diagnose skin cancers, understanding the benefit Mohs micrographic surgery can bring to your patients is essential in ensuring that they have the best possible long-term survival, cosmetic, and functional outcomes.