Mohs Micrographic Surgery is the most advanced and effective treatment procedure for skin cancer available today. Initially developed by Dr. Frederic E. Mohs, the Mohs procedure is a state-of-the-art treatment that has been continuously refined over 70 years. With the Mohs technique, physicians are able to see beyond the visible disease, to precisely identify and remove the entire tumor layer by layer while leaving the surrounding healthy tissue intact and unharmed. As the most exact and precise method of tumor removal, it minimizes the chance of re-growth and lessens the potential for scarring or disfigurement.
Our dermatologist is specially trained in surgery, pathology, and reconstruction, Mohs surgery has the highest success rate of all treatments for skin cancer - up to 99 percent. The Mohs technique is also the treatment of choice for cancers of the face and other sensitive areas as it relies on the accuracy of a microscopic surgical procedure to trace the edges of the cancer and ensure complete removal of all tumors down to the roots during the initial surgery. Mohs Micrographic Surgery is an effective and precise method for treating basal cell and squamous cell skin cancers.
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 therefore impossible to predict a final size until all surgery is complete. As Mohs surgery is used to treat complex skin cancers, approximately half of all treated tumors require 2 or more stages for complete excision.
Steps in detail
Anesthesia. The tumor site is locally infused with anesthesia to completely numb the tissue. General anesthesia is not required for Mohs micrographic surgery.
Stage I - Removal of visible tumor. Once the skin has been completely numbed, the tumor is gently scraped with a curette, a semi-sharp, scoop-shaped instrument. 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, "cautery", may be used to stop the bleeding.
Mapping the tumor. Once a "layer" of tissue has been removed, a "map" or drawing of the tissue and its orientation to local landmarks (e.g. nose, cheek, etc) 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 operative suite.
Additional stages - Ensuring all cancer cells are removed. 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 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 typically exceed 99% for new cancers, and 95% for recurrent cancers.
Reconstruction. Fellowship-trained Mohs surgeons are specially trained 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. Sometimes, a wound may be allowed to heal naturally.
Mohs micrographic surgery is distinct from routine surgical excision. With the Mohs technique, surgically removed tissue is carefully mapped, color-coded, and thoroughly examined microscopically by the surgeon on the same day of surgery. During this process, 100% of tissue margins are evaluated to ensure that the tumor is completely removed prior to repair of the skin defect. Mohs micrographic surgery therefore results in the highest cure rate for complex skin cancers while minimizing the removal of normal tissue.
The Mohs Surgery Process
The roots of a skin cancer may extend beyond the visible portion of the tumor. If these roots are not removed, the cancer will recur.
The visible tumor is surgically removed.
A layer of skin is removed and divided into sections. The ACMS surgeon then color codes each of these sections with dyes and makes reference marks on the skin to show the source of these sections. A map of the surgical site is then drawn.
The undersurface and edges of each section are microscopically examined for evidence of remaining cancer.
If cancer cells are found under the microscope, the ACMS surgeon marks their location onto the "map" and returns to the patient to remove another layer of skin - but only from precisely where the cancer cells remain.
The removal process stops when there is no longer any evidence of cancer remaining in the surgical site. Because Mohs surgery removes only tissue containing cancer, it ensures that the maximum amount of healthy tissue is kept intact.
Sources: American College of Mohs Surgery and University of California, San Francisco School of Medicine.