May 24, 2016
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Mohs Surgery

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What is Mohs micrographic surgery (MMS)?

Mohs micrographic surgery is a special technique that uses local anesthesia (numbing) to remove skin cancers. The majority of cases are performed in the physician's office. Mohs is a very precise, highly detailed method whereby horizontal pieces of tissue are cut from the bottom-most layer layers of the tumor and immediately stained and examined under the microscope. Repeated saucer-shaped layers of tissue are removed and examined until no more skin cancer can be microscopically visualized in the sample.

The procedure uses frozen sections of skin that are then stained with special dyes. The dyed frozen pieces of skin are examined under the microscope and a tumor map showing the sites of any residual cancer cells is drawn by the Mohs surgeon. The process allows an immediate examination of the entire tumor margin and tissue histology (microscopic examination of cells). If more cancer cells are seen under the microscope, then another skin layer is removed and again examined. Each skin layer that is removed is called a "level." If no more cancer cells are seen, then it is called "clear" (no more tumor) and no additional levels are needed.

By removing only tissue where cancer is known to be present, the technique combines a very high cure rate with excellent preservation of normal skin. Once the cancer has been fully removed, the Mohs surgeon looks at the wound to determine the type of repair for the best cosmetic result. Occasionally, the Mohs surgeon may refer patients to another physician to close the cancer-free wound.

Mohs is special because the entire edge and under-surface of each skin cancer layer is carefully microscopically examined for the presence of cancer cells. Traditional surgical pathology techniques using standard sections (bread loafing), only is able to evaluate 1%-3% of the tumor margins thereby increasing the chances that a small tumor cluster might be missed and left behind. Mohs enables the examination of 100% of the entire tumor's margin thereby reducing the chance that tumor cells will be left behind.

Mohs surgery is significantly more labor intensive than conventional methods of treating skin cancers and as a result it is more expensive. This type of surgery is typically reserved only for certain situations, which include recurrent cancers that have not been cured by conventional techniques, large tumors, tumors that occur in cosmetically sensitive areas like the mid-facial tissues, and so called morpheaform basal cell cancers which are known to have a high recurrence rate.

Mohs is usually scheduled only on certain days in the doctor's office because of the required equipment, tissue stains (dye), and the presence of a histotechnologist for tissue processing. Most of these procedures are generally performed with the patient waiting in the office for the tissue to be "read" or interpreted by the Mohs surgeon.

Why is the procedure called Mohs?

Mohs is named after its inventor, Dr. Frederic Mohs, who first described the technique in 1941.

Site after the tumor roots were cleared
Site after the tumor cells were cleared
Post-op closure of the wound with sutures
Post-op closure of the wound with sutures
Medically Reviewed by a Doctor on 6/8/2015



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