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March 2010

High Cure Rates for Skin Cancer With Mohs Surgery

Isaac Neuhaus, M.D.
Dermatologic Surgeon
UCSF Dermatologic Surgery and Laser Center

About 96 percent of the 1.3 million new cases of skin cancer diagnosed each year in the United States is basal cell or squamous cell carcinoma. When treating these cancers, Mohs micrographic surgery has typical cure rates of more than 99 percent for new skin cancers and 95 percent for recurrent skin cancer.

The Mohs surgical process involves a series of 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 below normal appearing skin. In many cases, it is impossible to predict a tumor size until all surgery is complete. As Mohs surgery is used to treat complex skin cancers, about half of the tumors require removing two or more layers of tissue for complete excision.

Step 1 — Anesthesia

The tumor site is locally infused with anesthesia to completely numb the tissue. General anesthesia is not required.

Step 2 — Removal of Visible Tumor

Once the skin is numbed, the tumor is gently scraped with a curette. This helps define the clinical margin between tumor cells and healthy tissue. The first thin, saucer shaped "layer" of tissue is then surgically removed by the Mohs surgeon. An electric needle may be used to stop bleeding.

Step 3 — Mapping the Tumor

Once a "layer" of tissue has been removed, a "map" or drawing of the tissue and its orientation to local landmarks, such as the nose and cheek, 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 about an hour to process, stain and examine a tissue section. During this processing period, the wound is bandaged.

Step 4 — Remove Additional Tissue

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.

This selective removal of tumor allows for preservation of much of the surrounding normal tissue. Because the systematic microscopic search reveals the roots of the skin cancer, Mohs surgery offers the highest chance for complete removal of the cancer while sparing the normal tissue.

Step 5 — Reconstruction

Fellowship-trained Mohs surgeons are experts in the reconstruction of skin defects. Reconstruction is individualized to preserve normal function and maximize aesthetic outcome. The best method of repairing the wound following surgery is determined only after the cancer is completely removed, as 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 designed. In some cases, a wound may be allowed to heal naturally.

UCSF Dermatologic Surgery and Laser Center

The UCSF Dermatologic Surgery and Laser Center specializes in diagnosing and treating a full spectrum of skin diseases and cancers and is a national leader in Mohs surgery.

The center has specialists that treat aggressive and unusual tumors and has a tumor board — including experts in dermatology, otolaryngology, plastic surgery and radiation oncology — that meets to discuss treatment options for complex patients. The tumor board ensures that high-risk patients with difficult neoplasms get the most appropriate treatment.

Other Resources

For more information, contact the Physician Referral Service at UCSF Medical Center:

Phone (888) 689-UCSF or (888) 689-8273
Email referral.center@ucsfmedctr.org