Mohs Surgery
Medical Author: Nili N. Alai, MD, FAAD
Medical Editor: William C. Shiel Jr., MD, FACP, FACR
What is Mohs micrographic surgery (MMS)? Why is the procedure called Mohs?
Mohs micrographic surgery is a
minor surgical procedure and special method of removing skin cancers using local
anesthesia (numbing). The majority of cases are performed in the physician's
office. Mohs is a very precise, highly detailed technique whereby small layers
of skin are sequentially removed and immediately examined under the microscope
until the samples indicate that the skin cancer is completely removed.
The procedure uses frozen sections of skin that are then stained with special
dyes. The dyed frozen pieces of skin are further examined under the microscope
and a tumor map is drawn by the Mohs surgeon. The freezing process allows an
immediate examination of the entire tumor margin and tissue histology
(microscopic examination of cells).
If more cancer cells or "roots" 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 roots 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 good preservation of normal skin. Once the
cancer has been fully removed, the Mohs surgeon looks at the wound to determine
the method to obtain the best wound repair and cosmetic result for you.
Mohs is special because the entire edge and undersurface of each skin cancer
layer is carefully examined under the microscope for the presence of very small
cancer cells. With regular or traditional surgery, only about 1%-3% of the
tumor margins are actually examined, thereby increasing the chances that a small
tumor root would be missed and left behind. Mohs allows for examination of 100%
of the tumor margins thereby reducing the chance that tumor cells will be left
behind.
Mohs is usually scheduled only on certain days in the doctor's office because
of the required equipment, tissue stains (dye), Mohs technologists, and
microscopes. 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.
Mohs is named after its inventor, Dr. Frederic Mohs,
who first described the technique in 1941.
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| From top: (top) Basal cell carcinoma on the neck; (middle) site after the tumor roots were cleared; (bottom) post-op closure of the wound with sutures |
Next: Where can I have Mohs surgery, and how long does the surgery take? »
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