Q&A: Mohs Surgery for Some Skin Cancers

Deborah F. MacFarlane, M.D., professor in the Department of Dermatology at MD Anderson
answers questions about Mohs surgery as treatment for some skin cancers.

What types of cancer is Mohs surgery used for?
Mohs is most often used for those patients with basal or squamous cell carcinomas that appear in areas of the body where tissue conservation is especially important. This includes tumors on the face, head or neck, fingers and genitals.

How accurate and effective is the Mohs procedure?
The Mohs technique uses precise tissue mapping to examine horizontally oriented sections of the tumor. During surgery, the tumor is mapped and tracked stage by stage so that we maximize the amount of tumor removed and minimize the amount of normal tissue removed. With each stage, we test 100% of the peripheral and deep tissue margins until it is clear, so we can guarantee approximately 98% to 99% of the time (for previously untreated tumors) that the tumor won't come back. This way we are able to leave minimal defects of scars.

Mohs surgery is an outpatient procedure that is typically completed all in one day. What is involved in the process?
When a patient comes in for the procedure, we first examine the cancerous area and mark where we will remove the tissue. The surrounding area is then numbed using a local anesthetic, and once the tissue is removed, we make a map of it. The tissue is given to a histotechnician, who stains it in our onsite lab and freezes it. The tissue is then cut into horizontal sections and placed on slides for microscopic examination.

If the margins are not clear of cancer, the surgeon will remove more tissue from the patient in the mapped area where the tumor appeared. This process, which can sometimes require several stages of tissue removal, is repeated until there is no remaining tumor and all of the margins are clear. The wound is then reconstructed and sewn up, and the patient is released. Some patients return here for suture removal. Other patients are followed by their referring doctors.

What kind of reconstruction options do patients have after Mohs?
In most cases, the surgeon reconstructs the wound on the same visit. In cases where the tumor is more complex, the patient may prefer to have plastic surgery, which is arranged prior to his or her planned Mohs procedure appointment.

Which patients can benefit the most from Mohs surgery? When is it the ideal choice for surgical procedures?
Patients with non-melanoma cancers in areas where tissue conservation is important are ideal candidates for the Mohs procedure. A lot of patients at MD Anderson are immunocompromised, so they are more prone to developing skin cancer. In particular, organ transplant recipients, patients with leukemia or lymphoma, or those who have received radiation have an increased risk of developing skin cancer. A lot of elderly patients or sick patients also benefit from Mohs surgery because it uses a local anesthetic instead of general anesthesia, which can sometimes pose risks to them. In such cases, Mohs surgery is often the best choice for treatment.