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JAMA Dermatology Patient Page
May 6, 2020

What Is Mohs Surgery?

Author Affiliations
  • 1Department of Dermatology, University of Pennsylvania, Philadelphia
  • 2Department of Dermatology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
JAMA Dermatol. Published online May 6, 2020. doi:10.1001/jamadermatol.2020.0039

Mohs surgery is a specialized type of surgery used to remove both common (ie, basal cell carcinoma, squamous cell carcinoma, melanoma) and rare skin cancers.

Mohs is the last name of the person who invented the technique: Frederic Mohs, MD. Mohs surgery is highly effective at removing skin cancer because the edges of the removed cancer tissue are checked much more thoroughly under the microscope than with regular surgery. In addition to being effective, the Mohs procedure allows the surgeon to leave behind normal skin and remove less healthy tissue.

Mohs surgery is not necessary for all skin cancers, but it is useful when:

  1. The location of the skin cancer is near areas that are important for daily activities, like the fingers, or for appearance, like the nose;

  2. Earlier treatments have not worked;

  3. A tumor is large; and

  4. Regular surgery is less likely to remove the cancer.

Mohs surgery is usually done with the patient awake. The tumor and the skin around it are numbed with injections of anesthesia. The Mohs surgeon removes the skin cancer that can be seen with the naked eye and takes it to a laboratory nearby. After the laboratory makes microscope slides with the removed skin cancer tissue, the Mohs surgeon looks under the microscope to check for any cancer cells left along the edges of the tissue. The microscope can help the surgeon find cancer that is small, hidden, or deep under the skin. If more cancer is found, the surgeon then removes more tissue along the sides or deep edge where the cancer is still present. This tissue is again processed by the laboratory and rechecked under the microscope by the Mohs surgeon. The process continues until all of the cancer is cut out. Because it is not possible to know how many tries it will take to remove the entire tumor, patients should be prepared to be at the dermatology clinic or medical center for the entire day. However, most procedures take just a few hours (Video).

Video. What Is Mohs Surgery?

After all of the cancer is removed, the Mohs surgeon will talk with the patient about different ways to fix the wound. The wound can be left to heal on its own, can be stitched closed in a straight line, or may require a more complicated surgical procedure. Often the wound is closed the same day by the Mohs surgeon, but sometimes it is repaired by another surgeon on the same day or a different day. The surgeon who fixes the wound provides instructions on how to take care of it at home.

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Article Information

Published Online: May 6, 2020. doi:10.1001/jamadermatol.2020.0039

Conflict of Interest Disclosures: No conflict of interest disclosures were reported.

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