What is Mohs Micrographic Surgery?

In the early 1940′s, Dr. Frederick Mohs, Professor of Surgery at the University of Wisconsin, developed a form of treatment for skin cancers he called chemosurgery. The word “chemosurgery” is derived from the words “chemical” and “surgery.”

The procedure has been refined and improved upon so that most cases are done using fresh tissue omitting the chemical paste Dr. Mohs used. The procedure is now called Mohs Micrographic Surgery, “micro” because the procedure utilizes microscopes and “graphic” because the surgeon makes a map of the surgical site and the microscopic findings.

Our Mohs surgeons have sub-specialty surgical training in the technique and are Fellows of the American College of Mohs Micrographic Surgery and Cutaneous Oncology. Our team will help answer your questions, respond to your anxieties, assist in surgery, and instruct you in dressings and wound care after the surgery is performed. A technician, whom you may not even meet, performs the essential task of preparing the tissue slides which are examined under a microscope by the physician.

The surgery is performed as follows: the skin is treated with a local anesthetic so there is no pain; the tumor is scraped using a semi-sharp instrument called a curette; a thin piece of tissue is then removed surgically around the scraped skin and divided into pieces that will fit on a microscope slide; the edges are marked with colored dyes; a map or diagram of the tissue removed is made; and the tissue is frozen by the technician. A pressure dressing is then applied and the patient is asked to wait while the slides are being processed. The Mohs surgeon will then examine the slides under the microscope and be able to tell if any tumor is still present. If cancer cells remain, the Mohs surgeon is able to precisely locate them based upon his map. Another layer of tissue is then removed and the procedure is repeated until the Mohs surgeon is satisfied that the entire base and sides of the wound have no cancer cells remaining. This process ensures the complete removal of the cancer while preserving as much normal surrounding skin as possible. The removal, processing and interpretation of each layer of tissue takes approximately 1 hour. Only 15-30 minutes is spent in the actual surgical procedure, the remaining time being required for slide preparation and interpretation. It usually takes removal of 1-3 layers of tissue (stages) to complete the surgery. Mohs micrographic surgery is generally finished in one day. Sometimes a tumor may rarely be extensive enough to necessitate continuing surgery a second day.

At the end of Mohs Micrographic Surgery, you will be left with a surgical wound. This wound will be dealt with in one of several ways. The possibilities explained below include:

1. healing by spontaneous granulation
2. closing the wound or part of the wound with stitches
3. using a skin graft
4. using a skin flap

Healing by spontaneous granulation involves letting the wound heal by itself. This offers a good chance to observe the wound as it heals after removal of a difficult tumor. Experience has taught us that there are certain areas of the body where nature will heal a wound as nicely as any further surgical procedure. There are also times when a wound will be left to heal knowing that if the resultant scar is unacceptable and some form of reconstruction can be performed at a later date. In this way a less complex reconstruction may be possible as any new scar shrinks up to 50% in a year.

Closing the wound with stitches is often performed. This involves some adjustment of the wound and sewing the skin edges together. This procedure speeds healing and can offer excellent cosmetic results. For example, the scar can be nearly hidden in a wrinkle line.

Skin flaps involve movement of adjacent, healthy tissue to cover a Mohs defect. They are often chosen for complex cases because of the excellent cosmetic match of nearby skin.

Skin grafts involve covering a surgery site with skin from another area of the body. There are two types of skin grafts. The first is called a “split thickness graft.” This is a thin shave of skin, usually taken from the thigh or scalp, which is used to cover a very large surgical wound. This can either be a permanent coverage or temporary coverage before another cosmetic procedure is done at a later date. The second graft type is the “full thickness graft.” This graft provides a thicker layer of skin to achieve better cosmetic results. In this instance, skin is usually removed from behind or in front of the ear (the donor site) and stitched to cover the wound. The donor site is then sutured together to provide a good cosmetic result.

If your Mohs Micrographic Surgery is extensive or a functional impairment results, we may recommend you visit one of several consultant physicians. If you have been sent to us by another physician skilled in skin closures (for example, a plastic surgeon), he/she will take care of you after your cancer has been removed.

In summary, by microscopically pinpointing areas involved with cancer and selectively removing these tissues, the Mohs surgeon can successfully remove your skin cancer with the best cure rate and the least loss of normal tissue. A smaller wound also offers you the likelihood of a better final cosmetic result. Although every effort will be made to minimize the scar, you will be left with a scar of some kind. Mohs micrographic surgery is one of the few “no brainers” in medicine.
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