Mohs micrographic surgery is a technique that allows dermatologists to selectively remove areas involved with the skin cancer, while at the same time preserving the greatest amount of normal tissue possible. If surgical repair of the defect is necessary, it can be done with the knowledge that there is no tumor remaining. As a result, Mohs micrographic surgery is very useful for large tumors, tumors with indistinct borders, tumors near vital functional or cosmetic structures, and tumors for which other forms of therapy have failed.

Over 60 years ago, Frederick Mohs, MD, of Madison, WI developed a unique form of treatment for skin cancer called chemosurgery. Dr. Mohs applied a caustic chemical to “fix” (harden) the area involving the tumor so that it could be removed and traced to all of its edges. This often took several days.

Today, this surgery is performed using a “fresh tissue” technique that avoids the use of this caustic chemical and allows dermatologists to remove all of the tumor in one day.

In most cases, the following approximations can be achieved:

• If you have a primary basal cell carcinoma, there is about a 99% chance that you will be cured.
• If you have a primary squamous cell skin cancer, you can be about 95% certain you will be cured with Mohs micrographic surgery.

However, follow-up visits to detect the rare recurrence are very important. You should be seen at least once each year to rule out the possibility of recurrence and/or new cancer development.

Mohs micrographic surgery is performed in a procedure room under sterile conditions with a long-acting local anesthesia. Once anesthesia is complete, the visible portion of the tumor may be removed by scraping with a sharp instrument called a curette. Following the removal of most of the tumor, a thin layer encompassing the complete undersurface of the tumor is excised. That layer is then cut into small pieces and a map is drawn to identify the location of each piece. The edges of each piece are marked with colored dye to aid in orientation on a map. Each piece is then frozen and cut, stained, and examined under the microscope by Dr. Miller. Any areas in which the tumor is found are marked on the map and Dr. Miller returns to remove these areas. This procedure is repeated until no more tumor is found and the cancer is entirely removed. After each layer of tissue is obtained, oozing or bleeding vessels are cauterized or ligated with suture. A pressure dressing is applied. You may then rest in our waiting area with your family member or friend.

Mohs is a unique way of treating skin cancer. What makes it special is that it is the only method of examining the entire margin of the removed tissue to ensure that no cancer remains. Because of this, the cure rate is exceptionally high.

Normally, when a surgeon removes tissue and sends it to a pathologist, it is cut into sections like a loaf of bread. The pathologist examines a few representative slices of tissue from the excised tumor to determine if the margins appear clear. However, some tumors, like basal cell and squamous cell carcinoma of the skin, are capable of spreading by sending out small microscopic extensions. In order to not miss these extensions, there needs to be a comfortable safety margin when using this standard approach.

Dermatologists who perform Mohs surgery are trained to obtain and process the tissue in a completely different way. Instead of looking at the margins in 3 slices of bread out of a loaf of 200 like a pathologist does, the specimen is processed so that the entire margin is examined. This is done by processing the tissue like a saucer and then cutting it into sections where each sections represents a thin layer of the entire margin. While doing this, the dermatologist makes a map on the patient and of the tumor that makes it possible to keep track of where any remaining tumor is located. If cancer is still seen, another thin layer of skin is removed from that location. When the surgery is complete, we can have a much higher degree of certainty that the entire tumor has been completely removed.

In most cases, the amount of tissue removed is less than with a standard excision. It must be remembered though, Mohs Surgery is not performed for cosmetic reasons, it is performed to ensure complete removal of tumors and provide oncologic cure. There are times when the amount of tissue removed using Mohs Surgery is greater than a standard excision, BUT because of the nature of Mohs Surgery, this only occurs when the skin cancer had extensions or “roots” extending far beyond the tumor. If these roots are not removed, the tumor will recur and the surgery was a failure. So, if the defect left by Mohs is large, it is because that tissue had to be removed in order to obtain cure.

Dermatologists with specialized training in Mohs surgery are the only ones capable of removing the tumor and performing a complete pathologic analysis of the margin. For this reason, the highest rate of cure is obtained if the tumor is removed by a Mohs surgeon.

Once the tumor has been cured, a defect is left that must be repaired. Having a plastic surgeon repair this is definitely an option, and for some patients this is  best. When Dr. Miller feels that the defect left by the removal of the tumor is likely to be large, he often refers you to a plastic surgeon prior to your Mohs surgery to discuss this as an option. Sometimes you can get the best of both worlds- the highest possible cure rate via Mohs and the best possible repair via plastic surgery. We are happy to facilitate this.