Mohs Micrographic Surgery

Dr. Frederic Mohs developed Mohs micrographic surgery (MMS) in the 1930s and the procedure has been refined and updated for modern use. Dr. Mohs realized that skin cancer is like the “tip of the iceberg” and that what we see is only the outward manifestation, but that the cancer grows into the skin like the roots of a tree and is only visible with microscopic analysis. MMS gets to and removes the roots of nonmelanoma skin cancer.

What is Mohs surgery?

MMS is a specialized surgical technique for removing locally invasive, high-risk skin cancers. It is reserved for cancer removal in areas that are and provides the most cosmetically acceptable scars or for the most aggressive skin cancers. MMS is the least invasive and most effective treatment for nonmelanoma skin cancers. Reported five – year cure rates are 98% or greater for common nonmelanoma skin cancers. The high success rate is due to the fact that 100% of the margin is evaluated prior to surgical repair, compared to standard surgical excision technique where less than 1% of the margin is evaluated via a random sampling method. This eliminates the situation where the tumor was excised, the wound closed, and the tissue is sent to a pathologist for examination, only to discover that tumor cells still exist necessitating a second surgery.

How is Mohs surgery performed?

MMS is a highly specialized and precise procedure performed by fellowship-trained surgeons with advanced training who act as both surgeon and pathologist. At Phoenix Surgical Dermatology Group, a board-certified dermatologist with fellowship training in MMS and reconstructive surgery will perform your procedure. Mohs surgery is performed in an outpatient setting, at our state-of-the-art dermatology office in Phoenix, AZ, under local anesthesia.

The area to be treated is numbed, and the lesion is removed one layer at a time. It is then prepared with colored dyes and is examined under a microscope to identify and map the microscopic roots of the cancer. The procedure is repeated until no tumor cells can be detected under microscopic examination. The wound is then repaired to restore function and cosmesis. After the surgery you will wear a bandage until the sutures are removed 5-7 days later. Final results will not be seen until 12 months after surgery as the scar continues to improve with time.

The procedure takes about 3-5 hours in our outpatient office, however, most of the time is spent creating and reading the slides to determine if your cancer has been completely removed. While it can take several hours to ensure the tumor is removed, this process eliminates the need to overestimate the depth of the tumor and allows for preservation of the greatest amount of noncancerous tissues. The outcome is a significantly better cosmetic result with a lower chance of cancer recurrence.

Side effects include swelling, bruising, tenderness and tightness at the site while the tissue heals. This is normal and temporary. Complete healing can take up to 12 months depending on the extent of surgery. Risks are the same as with any surgical procedure.

When is Mohs surgery recommended?

This highly technical surgery is usually reserved for certain circumstances, specifically:

• To remove skin cancer near cosmetically sensitive areas, including the face, nose, lips, eyelids, ears, fingers, toes and genitals.
• When the tumor is large and has indistinct margins.
• When there is a high risk of recurrence.
• To remove a recurrent skin cancer.
• When the tumor is located near scar tissue.
• When the tumor is aggressive and fast growing.
• When the patient is immunosuppressed.

How will the skin be repaired or reconstructed after the skin cancer is removed?

Once Mohs margins are free of cancerous cells, the defect is analyzed to determine the optimal repair technique. Tumor characteristics, location and size of the defect, patient comorbidities, and aesthetic considerations guide the choice of the repair technique.

Many Mohs surgical defects can be repaired in a linear manner. Some wounds can be left to heal on their own. Larger defects in anatomically sensitive areas require repair with a skin graft or local flap. 

What are the advantages of Mohs surgery?

The Mohs technique offers several advantages over standard surgical excision and pathology processing:

• Better clinicopathologic management of skin cancer, as one clinician performs the excision of tumor, oversight of tissue processing, and interpretation of frozen sections
• 100% surgical margin evaluation using horizontal sections. In contrast, standard excision uses “bread loaf” vertical sectioning, which permits the evaluation of a small portion of the tumor margins.
• Maximal normal tissue preservation in cosmetically and anatomically sensitive areas.
• Immediate reconstruction of the defect in most cases.
• Lowest recurrence rates compared to all other cancer treatments.

What are the disadvantages of Mohs surgery?

The Mohs technique is extremely labor-intensive and requires a highly qualified fellowship-trained clinician with expertise in high-risk skin cancers, as well as an experienced histotechnician with specific training in Mohs frozen tissue processing, a fully certified Mohs laboratory, and well-trained nursing staff. At Phoenix Surgical Dermatology Group, we strive to be world-class at every level of this highly technical process. 

The technique is also a time-consuming process that requires patient cooperation and understanding. A typical procedure can last three to five hours, and complicated cases can take even longer. We recommend bringing reading materials, work, laptops or other items to keep yourself occupied during the day.

In addition to being a board-certified dermatologist and fellowship-trained Mohs surgeon from two of the nation’s leading programs, Dr. Ramin Fathi is the founder of Phoenix Surgical Dermatology Group. Phoenix Surgical Dermatology Group aspires to be a world leader in skin cancer management and surgery.