The Mohs surgical process involves a repeated series of surgical excisions followed by microscopic examination of the tissue to assess if any tumor cells remain. Some tumors that appear small on clinical exam may have extensive invasion underneath normal appearing skin, resulting in a larger surgical defect than would be expected. It is not possible to predict a final size until all surgery is complete. Approximately 2/3rds of all tumors treated with the Mohs surgery require 2 or more stages for complete excision.
Step 1: Anesthesia
The tumor site is locally infused with anesthesia to completely numb the tissue. You will be awake for the procedure; general anesthesia is not used.
Step 2: Removal of visible tumor (1st stage)
Once the skin has been completely numbed, the tumor is gently scraped with a curette to get a better sense of the clinical extent of the tumor. The first thin, saucer-shaped “layer” (or “stage”) of tissue is then surgically removed by the Mohs surgeon. An “electric needle” may be used to stop the bleeding. This process takes approximately 10-20 minutes.
Once a “layer ” of tissue has been removed, a “map” or drawing of the tissue and its orientation to local landmarks is made to serve as a guide to the precise location of the tumor. The tissue is labeled and color-coded to correlate with its position on the map. The tissue sections are processed and then examined by the surgeon to thoroughly evaluate for evidence of remaining cancer cells. It takes approximately 60 minutes to process, stain and examine a tissue section. During this processing period, your wound will be bandaged and you may leave the procedure room.
Step 3: Additional stages (if necessary)
If any section of the tissue demonstrates cancer cells at the margin, the surgeon returns to that specific area of the tumor, as indicated by the map, and removes another thin layer of tissue only from the precise area where cancer cells were detected. The newly excised tissue is again mapped, color-coded, processed and examined for additional cancer cells. If microscopic analysis still shows evidence of disease, the process continues layer-by-layer until the cancer is completely removed. By beginning early in the morning, Mohs surgery is generally finished in one day. Very rarely, a tumor may be extensive enough to necessitate continuing surgery a second day.
This selective removal of tumor allows for preservation of as much of the surrounding normal tissue as is possible. Because this systematic microscopic search reveals the roots of the skin cancer, Mohs surgery offers the highest chance for complete removal of the cancer while sparing normal tissue. Cure rates typically exceed 99% for new cancers and 95% for recurrent cancers.
Step 4: Reconstruction
Fellowship-trained Mohs surgeons are experts in the reconstruction of skin defects whose goal is to preserve normal function and maximize the cosmetic outcome with each reconstructions. The best method for repairing the wound following surgery can only be determined after the cancer is completely removed, as the size and shape of the final defect cannot be predicted prior to surgery. Stitches may be used to close the wound side-to-side, or a skin graft or a flap may be utilized. Occasionally, a wound may be allowed to heal naturally.
Although every effort will be made to offer the best possible cosmetic result, you will have a scar. It is not possible to surgically remove a skin cancer without a scar. The scar can be minimized by the proper care of your wound and will continue to improve and become less noticeable for up to 12 months after surgery.
Healing by spontaneous granulation (also called “second intent”) involves letting the wound heal by itself. There are certain areas of the body where the body will heal a wound as nicely as any further surgical procedures. The healing time depends on the size, depth and location of the wound.
Often, the surgical defect can be repaired by stitching it into a straight line (“linear closure”). This involves some adjustment of the wound and sewing the skin edges together. If possible, an attempt is made to hide the scar (within natural lines of your skin, for example). The scar is often longer than patients expect to ensure that the skin lays down flat (rather than “puckering”).
In situations where a linear closure is not possible, a skin flap may be utilized. Skin flaps involve movement of adjacent, healthy tissue to cover a surgical site. Where practical, they are chosen because of the excellent cosmetic match of nearby skin.
Skin grafts involve covering a surgical site with skin from another area of the body. There are three types of skin grafts. The first is called a split-thickness graft. This is a thin shave of skin, usually taken from the thigh or behind the ear, which is used to cover a surgical wound. The second graft-type is the full-thickness graft. This graft provides a thicker layer of skin to achieve desired results. In this instance, skin is usually removed from behind the ear or around the collarbone (the donor site), and stitched to cover a wound. The donor site is then sutured together to provide a good cosmetic result. A third type of graft uses skin and cartilage. This usually comes from the ear and may be used to repair defects of the nose.
In rare cases, when Mohs surgery is extremely extensive or when removal of the tumor results in functional impairment, we may recommend that you visit one of several consultant surgeons for reconstruction.