Mohs micrographic surgery is a specialized, in office, skin cancer surgery. It is most often performed for non-melanoma type skin cancers that meet certain size or location requirements. Mohs surgery has gained increasing popularity over the last twenty years because of its low recurrence rates and smaller surgical wounds. Fellowship trained Mohs surgeons complete a 1-2 year fellowship where they learn the diagnostic and surgical reconstructive skills necessary for such intricate work.
The advantages offered by Mohs surgery result from three essential techniques: horizontal tissue sectioning, narrow margins, and surgical mapping.
Horizontal tissue sectioning is the method by which tissue is prepared during Mohs surgery. Visible tumor is removed from the skin and transported to the lab where it is immediately frozen. Because of its inherent plasticity, the technician is able to manipulate the skin edges to lie even with the base of the specimen. The specimen is then cut horizontally, creating a transparent film that reveals the entire base and all skin edges in one layer. Traditional pathologic sectioning is performed in a vertical manner and creates only representative samples of the base . Areas between cuts are never truly examined.
The strict margin control offered by horizontal sectioning gives the Mohs surgeon the freedom to take small surgical specimens. Typical margins in conventional excisions are 5mm beyond visible tumor. In Mohs surgery, these margins are reduced to 2-3 mm.
The trade-off for small surgical specimens is a higher risk of residual tumor at the wound edge. This problem is alleviated by the use of surgical mapping techniques. When residual tumor is present, a second specimen is taken from the involved quadrant only. This process is continued until all margins are free of tumor.
Mohs surgeons are proficient at closing complicated wounds of the face. Local tissue flaps and skin grafts are commonly used to close defects. Other methods including dermabrasion and steroid injection are employed if revision of the scar after healing is desired.
Mohs surgery is appropriate for skin cancers of any size on locations where the cancer tends to recur easily (central face, scalp, ears, lips, near eyes). Mohs surgery is also indicated for any skin cancers greater than 2 centimeters in size, those that arise in scars, or those subtypes of skin cancer with more aggressive nature.
At UTMB, Mohs surgery is performed by Dr Richard Wagner and his rotating dermatology resident. Dr Wagner is the deputy chair of the department and head of the division of dermatologic surgery. He is Mohs Fellowship trained and has over twenty years experience in the field.
Patients generally arrive just before 9 am. The involved area of skin is anesthetized with a small needle using lidocaine. The first stage of surgery generally takes 10-15 minutes, then a bandage is placed over the wound and the patient waits in the lounge while the skin is processed. Processing takes 1 hour, and then the tissue is examined by the surgeon using a microscope. If the margins are positive the process is repeated.
Most repairs do not begin until early afternoon. They take anywhere from 10 minutes to an hour to complete. You should expect to be in the office until 4 pm. Wound care instructions are given, and pain medicines are dispensed as needed. Scheduled follow up visits usually occur one week later.
All dermatology residents spend 3 to 6 months (depending on class size) of their second year on the Mohs rotation. Surgeries are performed by the residents and Dr. Wagner. Senior medical students are present to assist, and Plastic surgery residents rotate through the service as well.
There is no fellowship in Mohs surgery offered at UTMB. This gives the dermatology residents a level of exposure seen at very few programs. In the last three years, graduates have all performed over 100 cases, making them well prepared for surgical fellowships or complicated surgical procedures in their practices.