Mohs Micrographic Surgery

ACMS LogoMohs micrographic surgery, an advanced treatment procedure for skin cancer, offers the highest potential for cure and recovery – even if the skin cancer has been previously treated. Mohs surgery is a state-of-the-art treatment in which the physician serves as surgeon, pathologist and reconstructive surgeon. The accuracy of a microscope ensures removal of skin cancer down to its roots. Dermatologists trained in Mohs surgery, can see beyond the visible disease to precisely identify and remove the entire tumor, leaving healthy tissue unharmed. This procedure is most often used to treat two of the most common forms of skin cancer: basal cell carcinoma and squamous cell carcinoma.

Mohs micrographic surgery has the highest cure rate of all treatments for skin cancer -- up to 99 percent (even if other forms of treatment have failed). Mohs surgery is the most exact and precise method of tumor removal. It minimizes the chance of regrowth and lessens the potential for scarring or disfigurement.

Other offices may perform frozen section excisions and send the issue to an outside lab. This is not Mohs micrographic surgery. If the doctor removing the skin cancer is not also reading the slides, you are not having Mohs surgery.


Developed by Frederic E. Mohs, M.D. in the 1930s, the Mohs micrographic surgical procedure has been refined and perfected for more than half a century. Initially, Dr. Mohs removed tumors with a chemosurgical technique. Thin layers of tissue were excised and frozen before being pathologically examined. He developed a unique technique of color-coding excised specimens and created a mapping process to accurately identify the location of remaining cancerous cells.

As the process evolved, surgeons refined the technique and now excise the tumor, remove layers of tissue and examine the fresh tissue immediately. The chemosurgical technique developed by Dr. Mohs is no longer used. This reduces the normal treatment time to one visit and allows for immediate reconstruction of the wound. The heart of the procedure -- the color-coded mapping of excised specimens and their thorough microscopic examination – remains the definitive part of the Mohs micrographic surgical procedure. Clinical studies have shown that Mohs micrographic surgery has a five-year cure rate up to 99 percent in the treatment of basal cell and squamous cell carcinomas. Other treatment procedures (scraping and burning, standard excision, or radiation) often prove ineffective because they rely on the human eye to determine the extent of the cancer. In an effort to preserve healthy tissue, too little tissue may be removed resulting in recurrence of the cancer. If the surgeon is overcautious, more healthy tissue than necessary may be removed causing excessive scarring.

Some tumors do not respond to common treatments, including those greater than two centimeters in diameter, those in difficult locations and tumors complicated by previous treatment. Removing a recurring skin cancer is more complicated because scar tissue makes it difficult to differentiate between cancerous and healthy tissue. Indications: Mohs micrographic surgery is primarily used to treat basal and squamous cell carcinomas but can be used to treat less common tumors including melanoma. Mohs surgery is indicated when:

  • the cancer was treated previously and recurred
  • scar tissue exists in the area of the cancer
  • the cancer is in an area where it is important to preserve healthy tissue for maximum functional and cosmetic result, such as eyelids, nose, ears, and lips
  • the cancer is large
  • the edges of the cancer cannot be clearly defined
  • the cancer grows rapidly or uncontrollably


The Mohs process includes a specific sequence of surgery and pathological investigation. Mohs surgeons examine the removed tissue for evidence of extended cancer roots. Once the visible tumor is removed, Mohs surgeons trace the paths of the tumor using two key tools:

  • a map of the surgical site
  • a microscope

Once the obvious tumor is removed, Mohs surgeons:

  • remove an additional, thin layer of tissue from the tumor site
  • create a "map" or drawing of the removed tissue to be used as a guide to the precise location of any remaining cancer cells
  • microscopically examine the removed tissue to check for evidence of remaining cancer cells

If any of the sections contain cancer cells, Mohs surgeons: 

  • return to the specific area of the tumor site as indicated by the map
  • remove another thin layer of tissue only from the specific area within each section where cancer cells were detected
  • microscopically examine the newly removed tissue for additional cancer cells

If microscopic analysis still shows evidence of disease, the process continues layer-by-layer until the cancer is completely gone.

This selective removal of only diseased tissue allows preservation of much of the surrounding normal tissue. 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 the normal tissue. Cure rates exceed 99 percent for new cancers, and 95 percent for recurrent cancers. The best method of managing the wound resulting from surgery is determined after the cancer is completely removed. When the final defect is known, management is individualized to achieve the best results and to preserve functional capabilities and maximize aesthetics. The Mohs surgeon is also trained in reconstructive procedures and will often perform the reconstructive procedure necessary to repair the wound. A small wound may be allowed to heal on its own, or the wound may be closed with stitches, a skin graft or a flap. If a tumor is larger than initially anticipated, another surgical specialist with unique skills may complete the reconstruction. Besides its high cure rate, Mohs micrographic surgery is also cost effective. In a study of costs of various types of skin cancer removal, the cost of the Mohs process was commensurate with the cost of other procedures, such as electrodesiccation and curettage, cryosurgery, excision and radiation therapy. Mohs micrographic surgery preserves the maximum amount of normal skin and produces smaller scars. Repairs are more often simple and involve fewer complicated reconstructive procedures.

With its high cure rate, Mohs surgery minimizes the risk of recurrence and eliminates the costs of larger, more serious surgery for recurrent cancers. Because the Mohs procedure is performed in the surgeon’s office and pathological examinations are immediate, the entire process can often be completed in a single day. The highly-trained surgeons that perform Mohs surgery are specialists both in dermatology and pathology. With their extensive knowledge of the skin and unique pathological skills, they are able to remove only diseased tissue, preserve healthy tissue, and minimize the cosmetic impact of the surgery. Only physicians who have also completed a residency in dermatology are qualified for Mohs micrographic surgical training.

The American College of Mohs Micrographic Surgery currently recognizes more than 50 training centers where qualified applicants receive comprehensive training in Mohs micrographic surgery. The minimum training period is one year. During this year, the dermatologist acquires extensive experience in all aspects of Mohs surgery, pathology and reconstructive surgery. Anyone anticipating skin cancer surgery and considering the Mohs procedure may contact the office of Michael J. Huether, M.D.