What Is Mohs Surgery

Mohs micrographic surgery, which is performed in our office using local anesthesia, is a state-of-the-art treatment for skin cancer in which the physician serves as a surgeon, pathologist, and reconstructive surgeon. It yields the highest cure rate of all skin cancer treatments, with cure rates approaching 99% for tumors that have not previously been treated. The procedure relies on the precision and accuracy of examining tissue under a microscope to trace and ensure removal of the skin cancer, which may have roots that extend beyond what is visible to the naked eye. In addition, the removal of healthy skin is minimized, resulting in the smallest possible surgical defect and thereby decreasing the potential for scarring.

Mohs micrographic surgery was developed by Frederic E. Mohs, M.D. in 1936 at the University of Wisconsin. In its original form, described as “chemosurgery”, the technique utilized a 20% zinc chloride fixative paste that was applied directly to the skin of the patient for fixation of the tissue. Subsequently, the involved skin was surgically removed by serial excision with microscopic control of the tissue margins.

Removal of tissue was performed in layers and color coded with dyes in order to orient specimens to the patient. Dr. Mohs created a unique technique of color-coding excised specimens and developed a mapping process to accurately identify the location of remaining cancerous cells. This original “chemosurgery” technique, which is no longer performed, was very painful and sometimes took days to complete.

The surgical procedure has been extensively refined over the last seven decades, but it still relies on the fundamental principles of color-coded mapping of excised specimens and their thorough microscopic examination. Surgeons now excise the tumor in layers and examine the fresh tissue immediately. This reduces the normal treatment time to one visit and allows for immediate reconstruction of the wound.

In 1967, the American College of Mohs Micrographic Surgery and Cutaneous Oncology was formed to recognize surgeons who have completed specific, certified training in the Mohs technique. The College also functions as a regulatory and certification body for over 60 Mohs fellowship training programs and provides a source of continuing education for more than 700 practitioners of Mohs Micrographic Surgery.

Effectiveness

Mohs Micrographic Surgery is primarily used to treat basal and squamous cell carcinomas. Mohs Surgery is indicated when:

• The borders of the cancer are poorly defined
• The cancer is large
• The cancer has recurred after a prior treatment
• The cancer has previously been incompletely removed
• The cancer is in an area where preservation of healthy tissue is paramount to achieve the best possible cosmetic and functional reconstructive outcome, such as the nose, ears, eyelids and lips
• The cancer has grown rapidly
• The cancer has aggressive microscopic features, such as morpheic, infiltrating, or micronodular
• The cancer tracks along nerves (perineural invasion)

The Procedure

The Mohs Micrographic Surgery procedure relies on a specific sequence of surgery and pathological investigation:

1. The surgeon identifies the visible skin cancer.
2. The skin cancer and surrounding skin are anesthetized using local anesthesia, which is injected using a small needle.
3. The visible skin cancer and a narrow margin of healthy-appearing skin are surgically removed with a scalpel and marked with reference points on the patient.
4. An anatomic map of the removed tissue is created, which will guide the surgeon to the precise location of any residual cancer cells.
5. The tissue specimens are labeled with dyes that allow the surgeon to reference the tissue seen on the microscope slides directly back to the specific location on the patient.
6. The pathology technician processes the tissue specimens in the office lab and procedures frozen section slides.
7. The slides are examined under a microscopic by the Mohs surgeon.
8. If any of the microscopic sections contain tumor (i.e., skin cancer cells), the map guides the surgeon to the precise location where tumor roots remain.
9. An additional layer of tissue is removed in the location of the roots, and the tissue is processed and examined as previously described.
10. The tumor resection follows the same step-by-step process until all microscopic sections are clear from cancerous cells.
11. At this time, the surgeon will discuss options for reconstructing the surgical defect with the patient.

Reconstruction

The best method for reconstructing the surgical wound is determined after the cancer has been completely removed and the extent of the surgical defect has been determined. The primary considerations are preservation of function and maximizing the aesthetic outcome. Small wounds may be allowed to heal on their own, or the wound may be closed with stitches. Facial wounds often require reconstruction with a skin flap, or sometimes a skin graft. Reconstructing a wound with a skin flap involves utilizing lax skin that is adjacent to the wound, whereas a skin graft is performed by removing skin from another area of the body. The benefits and risks of each option will be discussed with you at the time of your surgery.