Last updated: 11/24/2009

There are two types of Mohs surgery: fresh-tissue technique and fixed-tissue technique. Of the surgeons who perform Mohs surgery, 72% use only the fresh-tissue technique. The remaining surgeons (18%) use both techniques. However, the fixed-tissue technique...

is used in fewer than 5% of patients. The main difference between the two techniques is in the preparatory steps.

Fresh-tissue technique

Fresh-tissue Mohs surgery is performed under local anesthesia for tumors of the skin. The area to be excised is cleaned with a disinfectant solution and a sterile drape is placed over the site. The surgeon may outline the tumor using a surgical marking pen, or a dye. A local anesthetic (lidocaine plus epinephrine) is injected into the area. Once the local anesthetic has taken effect, the main portion of the tumor is excised (debulked) using a spoon-shaped tool (curette). To define the area to be excised and to allow for accurate mapping of the tumor, the surgeon makes identifying marks around the lesion. These marks may be made with stitches, staples, fine cuts with a scalpel, or temporary tattoos. One layer of tissue is carefully excised (first Mohs excision), cut into smaller sections, and taken to the laboratory for analysis.

If cancerous cells are found in any of the tissue sections, a second layer of tissue is removed (second Mohs excision). Because only the sections that have cancerous cells are removed, healthy tissue can be spared. The entire procedure, including surgical repair of the wound, is performed in one day. Surgical repair may be performed by the Mohs surgeon, a plastic surgeon, or another specialist. In certain cases, wounds may be allowed to heal naturally.

Fixed-tissue technique

With fixed-tissue Mohs surgery, the tumor is debulked, as described previously. Trichloracetic acid is applied to the wound to control bleeding, followed by a preservative (fixative) called zinc chloride. The wound is dressed and the tissue is allowed to fix for six to 24 hours, depending on the depth of the tissue involved. This period, called the fixation period, can be painful to the patient. The first Mohs excision is performed as described; however, anesthesia is not required because the tissue is dead. If cancerous cells are found, fixative is applied to the affected area for an additional six to 24 hours. Excisions are performed in this sequential process until all cancerous tissue is removed. Surgical repair of the wound may be performed once all fixed tissue has sloughed off—usually a few days after the last excision.