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Mohs Micrographic Surgery for Skin Cancer

More than a million Americans will be treated for skin cancer this year and about one in five will develop a skin cancer in their lifetimes. The number of cases diagnosed every year is increasing at near epidemic rates and will continue to do so for the foreseeable future. The other bad news is that most skin cancers occur on the face, and can be very disfiguring. If you were to find yourself in this unfortunate but ever more common situation, how would you design the ideal skin cancer treatment? What would you do to save face?

You would develop a technique that would do two very important things. First, it would remove the cancer. Second, the removal would involve the least amount of healthy tissue to ensure the smallest possible wound. Small wounds heal better that large wounds and obviously the best wound is the one that has no cancer in it.

As it happens, Dr. Frederick Mohs came very close to achieving this ideal treatment in the 1930s. With a few refinements over the years, the Mohs surgical technique is now the most precise and effective way to treat skin cancer. This has resulted in the very rapid increase of its use for all sorts of skin cancers. Mohs surgery’s popularity is likely to keep increasing as the number of skin cancers continues to rise and as more people become aware of the surgery’s advantage.

The Procedure's Elegance and Exactness:

What is Mohs surgery? It is the excision of a cancer from the skin, followed by the detailed mapping and complete microscopic examination of the cancerous tissue and the margins surrounding it. If the margins are indeed cancer-free, the surgery is ended. If not, more tissue is removed, and this procedure is repeated until the margins of the final tissue examined are clear of cancer.

Mohs surgery thus eliminates the guesswork in the removal of skin cancers and pinpoints the cancer’s location when it is invisible to the naked eye. Mohs surgery differs from other techniques since the microscopic examination of all excised tissues during the surgery eliminates the need to “estimate” how far out or deep the roots of the skin cancer go. This allows the Mohs surgeon to remove all of the cancer cells while sparing as much normal tissue as possible.

The cure rate of the Mohs technique is 99 percent for most skin cancers, considerably higher than that of other methods; it also provides the greatest chance of cure when other methods have failed.

But don’t other techniques also use the microscope to make sure all of the cancer is removed?  Some do and some don’t. In those that do, not nearly as much of the tissue margin is examined as in the Mohs procedure.  Furthermore, the report establishing whether the treatment was successful is often not available until after the wound has been stitched. Thus, if the margins are involved, the wound will have to be reopened. Without immediate examination of the excised tissue, it is difficult and, indeed, risky for the non-Mohs surgeon to make the wound as tiny as possible by taking very narrow margins around the cancer. Therefore, in other types of excisions and destructive treatments, it is routine to treat well beyond the visible edges of the cancer. This leads to potential destruction of normal skin, a larger wound, more scarring, and a higher chance of recurrence than with Mohs surgery.

Controlling Size and Depth:

There is another advantage of Mohs surgery: With the careful microscopic examination of all tissue edges, the Mohs surgeon can tailor the size and depth of the surgery. For instance, if the surgeon suspects the cancer is thin and non-invasive, then a very thin excision of tissue is taken. If the cancer proves to be invasive, no problem! The cancerous cells will immediately be detected by the microscope and thanks to the meticulous mapping technique so crucial to Mohs surgery, the precise location of the remaining cancer cells will be determined. Subsequent excision involves just the skin that is known to still contain cancer. This result in some wounds so shallow rather than large not only eliminates some surgery that would otherwise be necessary but also saves patients valuable skin.

Another little known benefit of Mohs surgery is that in many cases both the removal of the cancer and the repair of the wound is accomplished on the same day. Some of the less complicated skin cancers can even be treated in as little as a few hours.

Time Lost or Saved?

There is another advantage of Mohs surgery: With the careful microscopic examination of all tissue edges, the Mohs surgeon can tailor the size and depth of the surgery. For instance, if the surgeon suspects the cancer is thin and non-invasive, then a very thin excision of tissue is taken. If the cancer proves to be invasive, no problem! The cancerous cells will immediately be detected by the microscope and thanks to the meticulous mapping technique so crucial to Mohs surgery , the precise location of the remaining cancer cells will be determined. Subsequent excision involves just the skin that is known to still contain cancer. This result in some wounds so shallow rather than large not only eliminates some surgery that would otherwise be necessary but also saves patients valuable skin.

Another little known benefit of Mohs surgery is that in many cases both the removal of the cancer and the repair of the wound is accomplished on the same day. Some of the less complicated skin cancers can even be treated in as little as a few hours.

When to Use Mohs:

If Mohs surgery provides the highest cure rate with the smallest loss of skin, why would anyone have a skin cancer treated any other way? Well, not all tumors require Mohs surgery.

Few skin cancers cannot be treated with Mohs surgery, especially when it may give the individual an advantage to do so. So, if the cancer is recurrent or large, is in a delicate area of the face, hands or feet, or is considered an “aggressively growing” type, the benefit of microscope-based removal has obvious advantages. Beyond that, if keeping the wound as tiny as possible or having confidence that the cancer has been removed by the procedure with the highest cure rate is important, then any tumor may benefit from Mohs surgery. On the other hand, of the chance of recurrence or the size of the wound is less important, quicker and less involved treatments may be preferred. For some small or less aggressive cancers, or those located in areas of the body known be easier to treat, the cure rates of other treatments can be nearly as good as with Mohs surgery, and therefore those treatments are reasonable to consider.

Another reason that Mohs surgery may not be chosen is that some cancers are more difficult to examine microscopically than others. One such cancer has been melanoma, the most dangerous of the skin cancers. In recent years, however, efforts to improve and refine the Mohs surgeon’s ability to identify melanoma cells have resulted in the development of special stains are known as immunocytochemistry stains and use substances that preferentially stick to the pigment cell, where melanoma occurs, making these cells much easier to see with the microscope. More Mohs surgeons are now using this procedure with melanoma.

Mohs surgery can take the better part of the day, while other procedures can be done more quickly. But again, these other procedures either do not evaluate only a small fraction of the total margin of skin removed, or examine the excised tissue days after the wound has been stitched. In the event that cancer remains in the wound, a second surgery will be necessary and the exact location of the remaining cancer may still not be known. When the treatments that do not examine the skin for adequacy of removal are performed, the only way of knowing whether the removal was successful is to wait and see if the cancer comes back.

Thanks to the ingenuity of Dr. Mohs and his technique, surgeons can provide the highest cure rates while making the smallest wounds. Even though skin cancers can often be very difficult to see, Mohs surgeons have no need to worry since they use a microscope. And this is how Mohs surgeons save face.

Cynthia Rogers, MD
8503 S. US 1, Ste 9
Port St. Lucie, FL 34952
Phone: (772) 398-3376
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