What is Mohs surgery

Mohs micrographic surgery is a highly specialized outpatient procedure which allows a physician to remove skin cancers. The technique, created by Dr. Frederick Mohs, originally used a fixative paste to fix the tissue. This was later modified with the advent of frozen section processing and is technically known as modified Mohs technique. This technique requires a lab capable of performing frozen sections and histologic slide preparation. The basic steps are as follows:

• The skin cancer  is identified then localized via physical examination
• A local  anesthetic (usually lidocaine) is injected around the skin cancer. 
• The tumor is  then debulked utilizing a curette. This allows the surgeon to appreciate any extension of the tumor  that wasn’t obvious before. 
• The physician  then removes a thin layer of tissue that encompasses the periphery and the  deep aspect of the apparent edges of the skin cancer. 
• The tissue is  then sectioned into smaller pieces to make slide preparation easier. These smaller pieces are then dyed,  which helps the surgeon keep the specimens oriented once they are  transferred to slides. This helps  to distinguish between top and bottom and left from right.   A  drawing is made so that the physician can pinpoint any areas of tumor that  crosses the excised border. This  drawing is called the Mohs map.
• These pieces  are then frozen and thin slices are taken from the underside of the pieces  and placed onto slides. 
• The slides are placed into a tissue stainer, which makes microscopic examination of the tissue possible. This stains the tissue and allows for the differentiation of normal cells and cancerous cells. 
• The slides are then examined by the Mohs surgeon with a microscope.
• After examining the edges and underside of the removed tissue, the Mohs surgeon outlines  the exact location of any areas of cancer. If more cancer is found, the      procedure is repeated in stages until the physician finds that no cancer      cells remain. 

The graphical representation to the right is offered to help further explain the process. 

Mohs Micrographic Surgery is just one of a number of techniques to treat skin cancer. Many skin cancers can be treated with superficial destruction, standard margin excision or radiation therapy. Each method has its place and your doctor can help you to determine which is right for you. But not all skin cancers are created equal. Some skin cancers require a method that ensures complete tumor removal to minimize your risk of a recurrence, while minimizing excess tissue removal. 

Mohs Micrographic Surgery is designed to accomplish this goal. Mohs Surgery utilizes real time microscopic examination during the surgical removal of your cancer. This enables the surgeon to remove just what is needed to ensure that your tumor is completely removed. This also enables your surgeon to make very small excisional layers, which reduces the removal of excess tissue. This makes repairing the surgical defect less complicated, which enhances your functional and cosmetic result. In contrast, standard methods utilize visual inspection to determine the extent of your cancer. While in many cases this is adequate, it may result in excessive or inadequate removal of skin. This may increase the chance of having your skin cancer recur or cause unnecessary scarring.

Mohs micrographic surgery allows for the highest chance of cure. In fact, while some other techniques have only a 60 to 90 percent success rate, Mohs enjoys a 98 percent or higher success rate in curing most skin cancers. By using the microscope and the mapping technique, Mohs surgery pinpoints the cancerous areas and removes those areas only. By doing this, the exact location of skin cancer cells is determined. This allows the physician to save as much healthy tissue as possible, allowing for a more functional and aesthetically appealing repair.

While the Mohs technique has its advantages, it isn’t required for every skin cancer. The Mohs technique is time consuming and technically difficult. Many skin cancers can be treated appropriately via other methods.

The types of skin cancers that are most likely to require Mohs surgery are as follows:

• Cancers that are located in critical anatomic  locations. These may be highly visible or cosmetically sensitive areas. These may also include areas where excess tissue in short supply or  areas that are known to heal poorly. The areas include the face, scalp, neck, ears, eyelids, lower legs, hands or feet. 
• Cancers that are large, aggressive, or rapidly growing
• Cancers that have been previously treated, but  that have come back
• Cancers that have poorly-defined or difficult  to visualize borders
• Cancers in which the highest cure rate is   desired
• Cancers in which the scar following removal  should be minimized