Overview of Mohs Surgery

August 1, 2019

Overview of Mohs Surgery

History of Mohs Surgery

Initially developed by Dr. Frederic E. Mohs, the Mohs procedure is a state-of-the-art treatment that has been continuously refined over 70 years. With the Mohs technique, physicians are able to see beyond the visible disease, to precisely identify and remove the entire tumor layer by layer.

Benefits of Mohs Surgery

Mohs micrographic surgery is distinct from routine surgical excision. With the Mohs technique, Dr. Pennie surgically removes the tumor and carefully maps, color-codes, and thoroughly examines the tissue microscopically on the same day of surgery. During this process, she evaluates 100% of the tissue margin to ensure that the tumor is completely removed prior to the repair of the skin defect. Mohs micrographic surgery, therefore, results in the highest cure rate for complex skin cancers, up to 99 percent, while minimizing the removal of normal tissue.

The Procedure

The Mohs surgical process involves a repeated series of surgical excisions followed by a microscopic examination of the tissue to assess if any tumor cells remain. Some tumors that appear small on clinical exam may have extensive invasion underneath normal-appearing skin, resulting in a larger surgical defect than would be expected. It is therefore impossible to predict a final size until all surgery is complete. As Dr. Pennie utilizes Mohs surgery to treat complex skin cancers, approximately half of all treated tumors require 2 or more stages for complete excision.

Preparing for Surgery

Because Dr. Pennie performs Mohs surgery under local anesthesia in the comfort of her office, there is minimal preparation that needs to be done before surgery.

  • You may eat a normal breakfast and take all your usual medications.
  • You are welcome to bring a friend or family member with you to provide support during the procedure.
  • Most patients are able to drive home after the procedure and return to work the next day.

Steps in Detail

Step 1

Anesthesia. The process begins by using local anesthesia to completely anesthetize the area around the skin cancer. General anesthesia is not required for Mohs micrographic surgery, making the procedure and recovery time shorter.

Step 2

Removal of visible tumor. Once the skin has been completely numbed, the tumor is gently scraped with a curette, a semi-sharp, scoop-shaped instrument. This helps define the clinical margin between tumor cells and healthy tissue. Dr. Pennie then excises a thin, saucer-shaped “layer” of tissue around the tumor. An electric needle, “cautery”, may be used to stop the bleeding.

Step 3

Mapping the tumor. Once Dr. Pennie removes a “layer”, she uses colored dyes to map the tissue to serve as a guide to the precise location of the tumor. The tissue sections are processed onto microscopic slides, which Dr. Pennie examines to determine whether skin cancer cells are present. It takes approximately 60 minutes to process, stain and examine a tissue section. During this processing period, your wound will be bandaged.

Step 4

Additional stages – If Dr. Pennie observes any cancer cells present, she identifies the location and marks this on her map. She will remove an additional layer of tissue only in the area where the skin cancer is present, preserving the healthy skin. The newly excised tissue is again mapped, color-coded, processed and examined for additional cancer cells. Dr. Pennie continues the process layer-by-layer until the cancer is completely removed.

Step 5

Reconstruction. After the cancer has been completely removed, Dr. Pennie will discuss your options for healing and repairing the wound. As a fellowship-trained Mohs surgeon, Dr. Pennie is specially trained in advanced reconstruction. Reconstruction is individualized to preserve normal function and maximize aesthetic outcomes. The best method of repairing the wound following surgery is determined only after the cancer is completely removed, as the final defect cannot be predicted prior to surgery. Sutures are used to close the wound. Some wounds may be closed side-by-side in a simple line while others might require a flap to be designed or a skin graft placed. On occasion, a wound may be allowed to heal over naturally.

Sources: American College of Mohs Surgery for more information please log onto


Will it Hurt?

When we start the procedure, you will be given local anesthesia with a very small needle. Although everyone’s tolerance for pain is different, patients who undergo Mohs surgery find the procedure remarkably painless. We pride ourselves on being particularly gentle. When you go home, you may be given a prescription for pain medication. Most patients report that they did not need it.

Will There be a Scar?

Yes. It is impossible to undergo surgery without having a scar. Nevertheless, it is our commitment that you will be completely satisfied with the cosmetic outcome. This means that, in some instances, it may take extra post-operative corrective procedures to attain the desired goal. We are committed to that process.

What Will the Scar Look Like?

Everybody heals at a different rate and the scar will look different over time. Initially, it will be red and bumpy, but eventually, the scar will be a barely visible “hair-thin” white line. We typically camouflage the scar in the lines of facial expression or your natural skin folds.

Will I Need Plastic Surgery?

Dr. Pennie performs the reconstructive surgery on site. She has been specially trained in advanced reconstruction after the Mohs procedure. In some instances, if the cancer involves the eyelids or the reconstruction requires you to be put to sleep, she will work with other specialists to coordinate your reconstruction.

Can I Go Back to Work After the Procedure?

We recommend that you go home and take it easy. Although the surgery takes place in a surgical setting with the use of local anesthesia, we have found that patients often feel “drained” after the procedure. Furthermore, any activity that puts strain on your surgical site or causes your blood pressure to elevate is contraindicated and could compromise the way you heal.

When Can I Exercise?

The resting period that we recommend after your surgery depends on where your cancer is located. Typically, we recommend that you do not exert yourself for one week if your cancer is on your head or neck area. This restriction is increased to two weeks when your cancer is on the trunk and extremities. Our doctor may recommend even longer restrictions for certain types of exercise. Make sure you ask us about the specific exercise you intend on doing.

Will My Insurance Cover This Procedure?

Absolutely! This is a medically necessary procedure.

Can I Drive Home?

Unless you have had surgery near the eye or on your hands, it is reasonable to expect that you can safely drive home. Of course, it is always comforting to have someone give you a ride.

Can You Do Multiple Surgeries at the Same Time?

We do not perform multiple surgeries on the same day. In general, the chances of getting an infection increase when multiple surgeries are done at the same time.

What if I Did Not Have This Treated?

If you have been diagnosed with skin cancer, it is important that you understand what would happen if this tumor was left untreated. There are three types of cancers that we deal with most commonly: Basal Cell Carcinoma, Squamous Cell Carcinoma and Melanoma. An untreated Basal Cell Carcinoma is cancer that would continue to grow at a relatively slow rate. Even if it seems to you that the biopsy took it all away, it has little extensions under the skin and it would grow in that direction. Eventually, it could become larger, bleed and be painful and/or disfiguring. In rare cases, it could grow down a nerve and lead to death. Basal Cell Carcinomas do not spread to other parts of the body (metastasize). Unlike a Basal Cell Carcinoma, an untreated Squamous Cell Carcinoma can metastasize. The same holds for a Melanoma, and it can do so rapidly.

Can I Postpone the Surgery?

We do not recommend doing so. Your skin cancer should be addressed as soon as possible. It is important that you keep your appointment and not reschedule so as not to delay your treatment. When we schedule your procedure, we reserve a 4-hour space. It is very difficult for us to find another one on short notice. Delaying surgery would allow your cancer to grow larger, making the reconstruction and your recovery more complicated. In the case of Squamous Cell Carcinomas and Melanoma, it may even lead to the spreading of the cancer.

Do I Need to Stop My Medications?

In general, we do not recommend that you stop any medications that were prescribed by a doctor without checking with that doctor. Over-the-counter medications containing aspirin, ibuprofen, or vitamins should be discontinued per our instructions.

Can I Die From This?

Squamous Cell Carcinomas and Melanomas can spread to other parts of the body and lead to death under certain circumstances. It is very rare to die from a Basal Cell Carcinoma. The concern with Basal Cell Carcinoma is that it can be disfiguring and lead to loss of function of nearby eyes or lips, etc.

Will I Be Put to Sleep?

No. All of our surgeries are done under local anesthesia, which is one reason why our procedures are so safe.

Can Someone be in the Surgery Room With Me?

Although we want you to feel as secure as possible while undergoing surgery, we reserve the right to determine who can be in the surgical suite based on our need for space or the complexity of the case

How Long Will it Take?

It is all dependent on the size and the site of your cancer. It is impossible to determine how long you will be with us until we have seen you. Even then, the cancer may be bigger under the surface and we would not know until we have started the procedure and Dr. Pennie has looked at your cancer under the microscope. Because of these uncertainties, we ask you to plan to be with us for at least 4 hours, although it may take much less time.

What Causes Skin Cancer?

People have skin cancer for multiple reasons. The two main reasons are sun exposure and genetics. Damaging sun exposure likely took place before you were 18 years old. Although it is very important that you protect yourself now from the sun so that you do not continue to get skin cancers, your current skin cancer is due to excessive sun exposure 20 years or so back. Also, your genetic background determines how likely you are to be affected by sun damage. If you have light-colored eyes, blond or red hair, and fair skin, you are more likely to have skin cancer. If you or any of your family members have had skin cancer, you are also at a higher risk of developing skin cancer. For more detailed information, please visit or

Do I Need to Have the Doctor Look at the Site Before I Have Surgery?

Yes. Dr. Pennie will examine the site and determine whether Mohs surgery is the right treatment for you before you undergo surgery. In addition, Dr. Pennie will review your medical history and current medications. She will determine if you need to stop any medications prior to surgery or take antibiotics before your procedure.

Will I Have Sutures? Will I Have to Come Back and Have the Sutures Removed?

You can expect to have sutures under a pressure bandage when you leave us. We typically use two layers of sutures, one underneath the skin that dissolves and another on top of the skin that is removed in 1-2 weeks.

What Does a Fellowship-Trained Mohs Surgeon Mean?

Mohs micrographic surgery involves an additional one to two years of training after residency. The Mohs micrographic surgery fellowship match is coordinated through the San Francisco Matching Program (SF Match) along with 11 other specialty fellowship matches, including craniofacial surgery, facial plastic surgery, neurosurgery, ophthalmology and pediatric otolaryngology. There are approximately 49 training programs that offer Mohs micrographic surgery training in the United States. There are 63 fellowship-trained Mohs surgeons in Florida. The American College of Mohs Surgery sponsors the fellowship-matching process. There is no substitute for additional formal training under the guidance of a mentor. Training in Mohs micrographic and reconstructive surgery cannot be mastered during short training periods such as preceptorship or residency and is best learned in a Mohs surgery fellowship.