Mohs Surgery

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What is Mohs surgery?

Mohs micrographic surgery is a surgical technique used to remove skin cancer. During Mohs surgery, the dermatologist acts as both the surgeon and the pathologist. The goals of Mohs surgery are to completely remove the skin cancer and to maximize conservation of normal tissue, resulting in high cure rates, optimal cosmesis, and preservation of function. Mohs surgery is recommended as first-line treatment for the majority of skin cancers that are aggressive and/or arising in high-risk patients and anatomic locations.

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How was Mohs surgery developed?

Dr. Frederic Mohs (1910–2002), of the University of Wisconsin, developed a tumor extirpation technique for skin cancer in the late 1930s. Initially, Mohs micrographic surgery involved chemically fixing in vivo cancerous tissue with zinc chloride paste. This tissue was then excised and systematically mapped, and frozen sections were examined under the microscope. The process was repeated if necessary to remove any residual malignancy until a completely tumor-free plane was achieved. Using the zinc chloride paste, each stage of Mohs took 24 hours, and the process was quite painful. In the early days, Mohs surgeons only removed the skin cancers and allowed the resultant defects to heal in over time (second intention healing), rather than performing surgical reconstruction.

Mohs FE. Chemosurgery: a microscopically controlled method of cancer excision. Arch Surg . 1941;42(2):279–295.

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Is Mohs surgery still performed with the zinc chloride chemical paste?

No. The Mohs technique has evolved to use fresh-frozen tissue methods. In the 1970s, the use of frozen sections alone in Mohs surgery was shown to have comparable cure rates to the use of zinc chloride paste. The elimination of zinc chloride paste allowed Mohs surgery to take place in a single day and avoided the pain associated with paste application. In addition, using only frozen sections made it possible for reconstruction of the Mohs defect to occur on the same day as tumor removal. Today, Mohs surgery is performed as a single-day, outpatient procedure and most commonly consists of tumor removal and pathology analysis followed by surgical defect reconstruction.

Stegman SJ, Tromovitch TA. Fresh tissue chemosurgery for tumors of the nose. Eye Ear Nose Throat Mon . 1976;55(2):26–30, 32.

Stegman SJ, Tromovitch TA. Modern chemosurgery—microscopically controlled excision. West J Med . 1980;132(1):7–12.

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What tumors can be treated with Mohs surgery?

The majority of tumors treated with Mohs surgery are basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), as these make up greater than 95% of skin cancers. However, Mohs surgery can also be used for melanoma (discussed later) and more rare cutaneous tumors. Less common tumors that have been demonstrated to have high cure rates with Mohs surgery (90% to 100%) include:

• Dermatofibrosarcoma protuberans (DFSP)

• Microcystic adnexal carcinoma

• Merkel cell carcinoma

• Sebaceous carcinoma

• Extramammary Paget's disease

• Atypical fibroxanthoma

• Malignant fibrous histiocytoma

• Desmoplastic trichoepithelioma

• Leiomyosarcoma

• Angiosarcoma

• Other adnexal carcinomas: primary cutaneous mucinous carcinoma, trichilemmal carcinoma, hidradenocarcinoma, eccrine porocarcinoma, squamoid eccrine duct tumor, pilomatrical carcinoma, and spiradenocarcinoma.

Thomas C, Woods G, Marks V. Mohs micrographic surgery in the treatment of rare aggressive cutaneous tumors: the Geisinger experience. Derm Surg. 2007;33:333–339.

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