Mohs Surgery

Skin cancer is the most common form of malignancy with over a million new cases diagnosed each year in the United States. Many patients with skin cancer have a history of chronic sun exposure. While not limited to any group of individuals, the typical skin cancer patient has a fair complexion (blue-eyed blondes or redheads), sunburns easily, and tans poorly. The main forms of skin cancer are basal cell and squamous cell carcinomas. These names refer to the type of cells in the skin from which the tumor arises. They are also referred to as non-melanoma skin cancers because they are not related in any way to melanoma. While some forms of squamous cell carcinomas have a potential to spread (metastasize) to distant parts of the body, generally both types of tumors stay localized to the skin. However, if left to grow, both types of skins cancer can invade deeply and destroy underlying structures such as cartilage and bone. Skin cancer, can be readily cured if diagnosed in the early stages of growth.

Some forms of skin cancer can invade deeply and are more prone to recur after conventional treatment. Dr. Frederick E. Mohs of the university of Wisconsin developed a method in 1936 to treat problematic skin cancers and still provide cures rates of 99% for previously untreated or primary tumors and 90-93% cure for previously treated or recurrent tumors. This method is called Mohs Micrographic Surgery.

The Mohs surgical procedure is generally performed in an outpatient setting under local anesthesia with the patient awake at all times, thereby avoiding the risks of general anesthesia.


The procedure begins with the Mohs surgeon anesthetizing the skin surrounding the tumor. The visible tumor is then removed with an instrument called a curette or with a scalpel. A very thin margin of normal appearing skin surrounding and underneath the tumor is then removed and brought to the laboratory where it is frozen and processed onto microscope slides. This is called the "first layer" or "first stage". A map is made of the tumor's precise location on the patient's skin.

The Mohs surgeon then examines the tissue under the microscope looking for any residual tumor. The entire outer margin and under surface is examined to ensure that no tumor is remaining deeper or wider in the skin. If the tumor is still present under the microscope, using the map, the mohs surgeon is able to pinpoint the area on the skin where the cancer is remaining. The patient is then brought back into the room and additional tissue is removed only in the area where tumor is remaining and the tissue is again processed and examined microscopically. The process is complete when the surgeon finds no residual tumor under the microscope.

While each stage or layer of the surgical procedure takes 15-20 minutes, the time required for the tissue to be processed in the laboratory can be 30+ minutes. Consequently the length of the procedure is dependent upon the number of stages necessary to remove all cancer cells. Patients can expect to spend several hours in the office on their surgery day.

Once Mohs surgery is completed, the wound may be allowed to heal on its own, or it may be closed with sutures (stitches). In some cases, the wound may need to be repaired with a skin flap or graft. The patient is given detailed wound care instructions in order to properly clean the surgical site at home. Depending on the type of stitches used, the patient my need to have the stitches removed or they may dissolve on their own. Either way, the patient is followed up closely to ensure proper healing of the wound.

Mohs surgery is one of the several methods for the treatment of skin cancer. The main advantage of Mohs surgery over virtually all other forms of therapy is that through microscopic examination of the tumor and its entire outer margin, the skin cancer can be traced out completely, providing the highest chance of complete cure. A second advantage is that the patient is waiting in the office while the tissue is being processed and examined by the surgeon. Any remaining tumor is removed the same day and the patient leaves the office knowing the tumor is completely removed. Because of the preciseness of the procedure, only a very small amount of normal skin is removed, which helps to minimize the size of the surgical wound and subsequent scar.

Mohs surgery is one of several methods for the treatment of skin cancer. It is indicated for certain aggressive types of skin cancer, cancers that have recurred after treatment, cancers that are near vital structures such as the eye, cancers in areas where tumors tend to recur (mid face, including nose), and areas where limited normal skin is present (ears). The Mohs surgeon will often treat tumors with other methods when appropriate.

In summary, Mohs Micrographic surgery has proven to be extremely effective method to treat skin cancer. Mohs surgeons have undergone extensive training which concentrates on all three aspects of the procedure including removal of the cancer, examination under the microscope, and reconstruction of the wound after complete tumor removal. The American College of Mohs Micrographic Surgery and Cutaneous Oncology has established educational requirements in order to maintain the high quality of Mohs Micrographic Surgery among its members. Members are required to complete a 1-2 year fellowship after residency at one of 50 approved fellowship training programs. Find out more about the Mohs College & Learn More about Mohs Surgery