A Mohs Surgeon Explains the Procedure

AIM at Skin Cancer recently interviewed Dr. Christensen about Mohs Micrographic Surgery.

What is Mohs surgery?

Mohs surgery is a very precise treatment for many types of skin cancers. The whole emphasis of Mohs surgery is to completely remove the skin cancer, while removing the least amount of healthy surrounding skin.

To achieve this goal, we use a comprehensive margin analysis. This means we look at all the edges and the base of the lesion to confirm that the cancer is completely removed, at the time of surgery. Looking at the edges of the tissue allows us an incredibly high cure rate of about 99%.

While attaining this high cure rate, we also minimize the amount of tissue we remove, allowing for a more favorable cosmetic outcome. These attributes of precision, complete margin analysis, high cure rates, tissue conservation and favorable cosmesis, make this a treatment of choice for most head and neck skin cancers.

What types of skin cancer can be treated with Mohs surgery?

Historically, Mohs surgery was used to treat nonmelanoma skin cancers. The most common types of non-melanoma skin cancer are basal cell carcinoma and squamous cell carcinoma.

Other nonmelanoma skin cancers are much less common, but may be treated using Mohs surgery. These skin cancers come from hair follicles, sebaceous glands, sweat glands, or other adnexal structures in the skin. Examples of these types include sebaceous carcinoma, desmoplastic trichoepithelioma, or microcystic adnexal carcinoma.

Recent studies have shown the effectiveness of Mohs surgery for some early stage melanomas. Under the appropriate circumstances and used in the right setting with melanoma-specific stains, Mohs surgery can be used to treat melanoma.

What is involved in Mohs surgery?

Mohs surgery is an outpatient procedure to remove the skin cancer. Before a referral for Mohs surgery, a patient has already had a biopsy. Their spot or lesion has received a pathologically confirmed diagnosis of skin cancer. The spot also has to fulfill set criteria of location, size, pathology subtype and patient risk factors to qualify. Then, they are referred for Mohs surgery for treatment.

When patients with skin cancer qualify for Mohs surgery, they come into the scheduled clinic where the procedure occurs. First, we introduce ourselves and discuss the procedure. Then, we will draw on the patient, identifying the site that will be removed.

For example, if their skin cancer is on the cheek, then I’ll draw around that spot. I will show the patient in the mirror. I tell the patient this is the spot I’m going to treat, and I even draw out what my repair will be. Of course, this is the most likely anticipated repair. The repair can change based on how much skin and tissue the cancer destroys and has to be removed during the surgery.

The next step is to numb the patient’s skin cancer site with local anesthesia. After the anesthesia, we clean and drape the area to prevent infection, and then we remove the area that’s obvious to our clinical eye. Then, we ink the tissue and we map it. The mapping allows us to maintain orientation and know which direction is up, down, right, or left when it is removed.

We put a bandage on the patient’s skin site, where we removed tissue, and they wait in the waiting room.

While the patient waits, we take the removed tissue to the lab. It takes us about an hour to process the tissue in the lab. We process the tissue by horizontally cutting the tissue. We cut the tissue sections so that they are very thin and fine. The tissue sections are tiny – only about five to seven microns thick. The tissue sections are methodically placed on the slides and stained to allow visualization of the cancer cells.

The doctor who surgically removed the cancer also analyzes it on the slides under the microscope. We will look at the stained tissue sections under the microscope and 100% of the peripheral margin to be examined. The tissue is placed on the slides in a specific order that allows assessment of the deep margin to determine if it is clear of suspicious cancer cells.

When I sit at my microscope, I see that the tissue which was inked with color, corresponds to the colors on the map of the tissue. In the included map example, cancer cells were seen by the green inked edge of the tissue, the middle deep tissue and the yellow ink edge of the tissue in the first stage (seemingly almost throughout the first stage removed, as shown by the red markings). More skin was removed in all these areas. This second stage showed persistent cancer cells at the superior edge. In the 3rd stage, skin was only removed at the superior edge and showed a small amount of persistent cancer cells at this superior edge. Then a 4th stage was removed and this was all clear of skin cancer cells.

If more tumor cells are observed on the slide, the patient will return to the procedure room. I come back to the room and we numb up the patient again. We remove more tissue again using the same process. We repeat where we take a little tissue, process it, and examine it.

We repeat this process of removing areas of skin where the cancer remains until the cancer is gone. About 50% of the time, we must return a second time on the patient and take more tissue. Another 50% of the time, we get it all the first time. Mohs is very precise.

During the whole process, there are two hard parts of the procedure for the patient: the numbing and the waiting. Nobody likes needles or the burn of the numbing medicine as it goes in, but it is tolerable and the discomfort lasts a short time.

The other hard part for the patient is waiting. I always remind the patient that an hour may seem like a long wait. Still, it’s so much better than a couple of days after having an excision and waiting for the report to come back.

In our practice, our Mohs brochure tells patients to come prepared to be with us for three to eight hours. I always say, in the end, we are going to get rid of your cancer.

What is the recovery process like after Mohs surgery?

The recovery after Mohs surgery can vary depending on how big the skin cancer is, what needs to be removed, and what the repair is. A small cancer treated may be allowed to heal by Mother Nature. The patient would have no restrictions in activity, but would keep the area clean, moist with Vaseline and covered until it has completely healed.

Some might need a simple closure where we do a line of stitches. These patients must have a bandage on the site and keep it moist, covered, and clean for a week, until their sutures are removed or dissolve. They will have activity restrictions during this time.

There might be longer recoveries if the procedure was a bit more involved. For example, if the patient lost a lot of structure of their nose from the cancer, we must reconstruct the nose. In this situation, we may have to take cartilage from their ear to bring back structure and cover that with a local or distant flap of skin to reconstruct the nose, like a flap of skin.

In some of these cases, there may be two stages for the reconstruction. The first stage is done on the day of the Mohs surgery, and the patient is left in a healing process with bandages for three weeks. The second stage is done three weeks later. These patients have restrictions in activity for a four-week period.

Most patients’ restriction consists of a 10-pound weight lifting restriction, avoidance of aerobic activities that increase heart rate of blood pressure and no bending with one’s head lower than their waist. For patients who work out every day, we tell them to replace their heavy workouts with a slow walk, to allow them to maintain their routines.

A lot of our patients have healed significantly in one week, but are truly looking better in a month. It’s a healing process, but usually, for the first week, everyone’s got bandages on and restrictions of not lifting, not bending, and limiting their cardiovascular workouts. It may take six months to one year for a scar to fully mature and become what it will be.

Conclusion

In conclusion, Mohs surgery is an extremely effective and safe technique. It is best performed in the hands of someone who has been properly trained to do it. That means the clinician has completed a fellowship and training and is board certified in Mohs surgery. The training and certification are important. It ensures the people who are helping patients make their healthcare decisions are qualified to help make those decisions. Skin cancer can be a scary diagnosis and we want to be sure that all patients are well cared for with the best techniques and in the hands of health care providers qualified to guide the best care decisions.