Mohs Micrographic Surgery


What is Mohs Micrographic Surgery?

Mohs micrographic surgery is a specialized, highly effective technique for the removal of skin cancer. The procedure was developed in the 1930s by Dr. Frederic Mohs at the University of Wisconsin and is now practiced throughout the world. Mohs surgery differs from other skin cancer treatments in that it permits the immediate and complete microscopic examination of the removed cancerous tissue, so that all “roots” and extensions of the cancer can be eliminated. Due to the methodical manner in which tissue is removed and examined, Mohs surgery has been recognized as the skin cancer treatment with the highest reported cure rate.

Special Qualifications of the Mohs Surgeon

Physicians performing Mohs surgery should have specialized skills in dermatology, dermatologic surgery, dermatopathology, and Mohs surgery. Basic and advanced training in Mohs surgery is available through selected Residency programs, specialized fellowships, observational preceptorships, and intensive training courses. In addition, the Mohs surgeon must have the required surgical and laboratory facilities and must be supported by a well-trained Mohs nursing and histotechnological staff. Your Mohs surgeon can provide you with detailed information regarding his or her training in the above disciplines, as well as all applicable professional affiliations.

Advantages of the Mohs Surgical Procedure

Some skin cancers can be deceptively large – far more extensive under the skin than they appear to be from the surface. These cancers may have “roots” in the skin, or along blood vessels, nerves, or cartilage. Skin cancers that have recurred following previous treatment may send out extensions deep under the scar tissue that has formed at the site. Mohs surgery is specifically designed to remove these cancers by tracking and removing these cancerous “roots.” For this reason, prior to Mohs surgery it is impossible to predict precisely how much skin will have to be removed. The final surgical defect could be only slightly larger than the initial skin cancer, but occasionally the removal of the deep “roots” of a skin cancer results in a sizeable defect. The patient should bear in mind, however, that Mohs surgery removes only the cancerous tissue, while the normal tissue is spared.

Special Indications for Mohs Surgery

It is important to note that Mohs surgery is not appropriate for the treatment of all skin cancers. Mohs micrographic surgery typically is reserved for those skin cancers that have recurred following previous treatment or for cancers that are at high risk for recurrence. Mohs surgery also is indicated for cancers located in areas such as the nose, ears, eyelids, lips, hairline, hands, feet, and genitals, in which maximal preservation of healthy tissue is critical for cosmetic or functional purposes.

The Mohs Surgical Procedure

Typically, Mohs surgery is performed as an outpatient procedure in the physician’s office. Although the patient is awake during the entire procedure, discomfort is usually minimal and no greater than it would be for more routine skin cancer surgeries. The Mohs surgical procedure is illustrated in the following diagrams:

Mohs Micrographic Surgery | Los Alamitos CA | Agoura Hills
Figure A
The area to be treated is cleansed, marked, and injected with a local anesthetic. The Mohs surgeon removes the visible cancer, along with a thin layer of additional tissue (Stage I). This procedure takes only a few minutes, and the patient waits while tissue is being processed and examined.
Stage 1

Mohs Micrographic Surgery | Los Alamitos CA | Agoura Hills
Figure B
The removed tissue specimen is cut into sections, stained, and marked on a detailed diagram (Mohs map).
Tissue cut in saucer shape

Mohs Micrographic Surgery | Los Alamitos CA | Agoura Hills
Figure C
Tissue is frozen on a cryostat, and technician removes very thin slices from the entire edge and undersurface. These slices are then placed on slides and stained for examination under the microscope. (This is the most time-consuming portion of the procedure, often requiring one hour or more to complete.)

Mohs Micrographic Surgery | Los Alamitos CA | Agoura Hills
Figure D
The Mohs surgeon carefully examines the entire undersurface and complete edge of the specimen, and all microscopic “roots” of the cancer are precisely identified and pinpointed on the Mohs map. Upon microscopic examination, if residual cancer is found, the Mohs surgeon utilizes the Mohs map to direct the removal of additional tissue (Stage II). Note that additional tissue is removed only where cancer is present.
Stage 2

Mohs Micrographic Surgery | Los Alamitos CA | Agoura Hills
Figure E
This process is repeated as many times as necessary to locate any remaining cancerous areas within the tissue specimen (Stage III, Stage IV, etc.)
Stage 3

Mohs Micrographic Surgery | Los Alamitos CA | Agoura Hills
Figure F
When microscopic examination reveals that there is no remaining tumor, the surgical defect is ready for repair.
Stage 4

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