Mohs Micrographic Surgery (Mohs Surgery)
Mohs Micrographic Surgery, performed by a fellowship-trained member of the American College of Mohs Surgery, is an advanced treatment for skin cancer that offers the highest cure rate - even if the skin cancer has been previously treated by another procedure. Mohs Micrographic Surgery is a state-of-the-art treatment in which the physician serves as surgeon, pathologist and reconstructive surgeon. It relies on the ability of a microscope to trace out and ensure removal of the skin cancer's roots. This procedure allows physicians who have completed a fellowship in Mohs surgery to see beyond the visible disease and to precisely identify and remove the entire tumour, leaving healthy tissue intact and unharmed. Mohs surgery is most often used to treat two of the most common forms of skin cancer: basal cell carcinoma and squamous cell carcinoma, however it is also an effective treatment for other types of skin cancer.
Clinical studies have shown that the cure rate for Mohs Micrographic Surgery is the highest of
all treatments for previously untreated basal cell carcinoma (99 percent ) and (95 percent) for
recurrent basal cell carcinomas. As the most exact and precise method of tumour removal, this
procedure minimizes the chance of recurrence and decreases the potential for scarring or
disfigurement. As such, Mohs surgery offers the highest potential for complete removal of
the cancer, while sparing the surrounding healthy tissue.
The Fellowship-Trained Mohs Surgeon
The American College of Mohs Surgery is the oldest professional organization of physicians who have attained extensive training and experience in Mohs Micrographic Surgery.One of the major goals of the Mohs College is to ensure the highest quality of training in Mohs surgery, which thereby ensures the highest quality of care for patients undergoing this procedure.
To be accepted as members of the Mohs College, physicians must complete a three-year
residency in dermatology or a related field, plus a one- or two-year fellowship program approved by the Mohs College that includes extensive training in Mohs surgery, pathology and reconstructive surgery. Currently more than 70 training centres around the United States are recognized by the Mohs College for instruction in Mohs Micrographic Surgery.
Physicians who have completed a Mohs-College-approved fellowship will, by virtue of their rigorous training, possess the skills and expertise necessary to perform Mohs Micrographic Surgery at all levels of complexity.
Developed by Frederic E. Mohs, MD, in the 1930s, the Mohs micrographic surgical procedure
has been refined and perfected for more than half a century. Initially, Dr. Mohs removed tumours with a chemosurgical technique, which entailed the application of a chemical to the tumour before tissue was removed. This process was time consuming and it was usually necessary to extend the surgery over the course of a number of days during which time, thin layers of tissue were excised, frozen and then pathologically examined. The surgery included a unique technique for colour-coding excised specimens and created a mapping process to accurately identify the location of remaining cancerous cells.
As the process evolved, surgeons omitted the chemical treatment and refined the technique so
surgery could be completed in one day. However, the colour-coded mapping of the excised
specimens and the thorough microscopic examination of excised tissue plus the fact that the
same physician acts as both surgeon and pathologist remains central to Mohs Micrographic
Surgery to this day and generally permits immediate reconstruction of the wound.
Common treatment procedures such as curettage, and electrodesiccation, cryosurgery, and
radiation therapy often prove less effective because they destroy the tissue and leave no
specimen for pathological examination. Standard surgical excision relies on the human eye and
examines only a fraction of the actual surgical margins for cancer, whereas Mohs surgery
evaluates 100 percent of the surgical margins. In an effort to preserve healthy tissue, too little tissue may be removed, which can cause the cancer to recur. It can also result in the removal of too much healthy tissue, resulting in unnecessary scarring.
Some tumours often do not respond well to common treatments, including those tumours greater than two centimetres in diameter, those in difficult locations and those complicated by prior treatment. Removing a recurrent skin cancer is more complicated because scar tissue may hide cancerous cells. In these cases Mohs surgery is the most appropriate treatment.
The Mohs process includes a specific sequence of surgery and pathological investigation. Mohs surgeons examine the removed tissue for evidence of cancer cells. Once the visible tumours is removed, Mohs surgeons trace out the paths of the tumours using two key tools:
Once the obvious tumour is removed, Mohs surgeons:
If any of the sections contain cancer cells, Mohs surgeons:
If microscopic analysis still shows evidence of disease, the process continues, layer-by-layer,
until the cancer is completely removed.
Mohs Micrographic Surgery is used primarily to treat basal and squamous cell carcinomas, but
can also be used to treat less common tumours.
Mohs surgery is indicated when:
The best method of managing the wound resulting from surgery is determined after the cancer
is completely removed. Once the final defect is known, management is individualized to achieve the best results and to preserve functional capabilities and maximize aesthetics. The Mohs surgeon is also trained in reconstructive procedures and usually will perform the reconstructive procedure necessary to repair the wound. A small wound may be allowed to heal on its own, or the wound may be closed with sutures, a skin graft or a flap. On some occasions another surgical specialist may complete the reconstruction as part of a team approach.
In addition to its high cure rate, Mohs Micrographic Surgery also has been shown to be cost
effective. In a study of costs of various types of skin cancer removal, the Mohs process was
found to be comparable to the cost of other procedures, such as electrodesiccation and curettage, cryosurgery, excision and radiation therapy.
In addition, Mohs Micrographic Surgery has other advantages: