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Mohs Micrographic Surgery: Procedure & Risks

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Mohs micrographic surgery is a method used to remove skin cancer. The procedure was developed by Frederic E. Mohs, M.D. in the 1930s and has since been refined.

Mohs micrographic surgery

What types of skin cancers are removed with Mohs surgery?

The Mohs procedure is most often used to treat basal cell and squamous cell carcinomas - two of the most common forms of skin cancer. However, there is also utility for other more rare, aggressive, skin and soft tissue cancers. Mohs surgery is particularly helpful for:

  • Skin cancers near vital functional or cosmetically important areas, such as eyelids, nose, ears, lips, forehead, scalp, fingers, or genital area.
  • Skin cancer that is 2 cm (approximately 1 inch) or larger on any area other than the face.
  • Skin cancer with borders that are not clearly defined.
  • Skin cancers in which other treatments have failed (i.e., the cancer comes back after treatment).
  • Skin cancer in areas where scar tissue already is present.

What are the steps in the procedure?

The Mohs procedure involves a layer-by-layer removal of skin that contains cancer cells. Here are the typical steps in the procedure:

  • The skin around the cancer cells is numbed with an injected anesthetic.
  • Any visible, raised area of the tumor is removed first.
  • A thin layer of tissue is removed from the involved site, with attempt to preserve as much healthy, normal skin as possible.
  • The tissue is marked in a manner to identify right, left, top, and bottom, which is also marked on a map of the patient.
  • The removed tissue is immediately frozen, cut, and stained in the doctor's office. This process takes approximately one hour, but this time varies from case to case.
  • The entire bottom and outer edges of the removed tissue layer are examined under a microscope by the Mohs surgeon.
  • If any cancer cells are seen under the microscope, their location is identified (according to the markings and map), and an additional thin layer of tissue is removed only from the area where cancer cells remain.
  • The process of microscopic examination and removal of additional layers of tissue continues until no more cancer cells are seen under the microscope.

Since the Mohs surgical technique only removes diseased tissue in the specific area in which it resides, more of the surrounding normal tissue can be saved. Another advantage of the Mohs technique is that the microscopic examination and removal method reveals the skin cancer down to its roots, allowing for complete removal of the cancer.

How successful is Mohs surgery?

Mohs micrographic surgery has the highest cure rate of all treatments for basal cell and squamous cell skin cancers. According to the American College of Mohs Surgery (ACMS), the cure rate exceeds 99 percent for new skin cancers and 95 percent for recurrent skin cancers.

Are there risks associated with Mohs surgery?

The complications associated with the Mohs surgery itself are very low; however, risks are unique to each individual. Please discuss your particular health issues and any concerns about the Mohs procedure with your surgeon. Listed below are the usual risks associated with Mohs surgery:

  • Scar formation at the site of tumor removal.
  • Larger than expected wound created upon removal of the skin cancer.
  • Poor wound healing, which may be due to the patient's underlying health conditions or failure of the wound repair method.
  • Excessive bleeding from the wound, which could affect wound healing and/or result in the need for more office visits.
  • Wound that becomes infected (an uncommon occurrence , minimized by using sterile technique).
  • Loss of nerve function (muscle or feeling) if a tumor invades a nerve, which can be temporary or permanent.
  • Regrowth of tumor after removal (more common with previously treated tumors and large, longstanding tumors).
  • Cosmetic or functional deformities if tumor is near or on an important structure such as eyes, eyelids, nose, ears, lips, forehead, scalp, fingers, or genital area.

Will I need reconstruction of the resulting wound?

After complete removal of the skin cancer, your surgeon will discuss the best method of managing the resultant wound. The choices include:

  • Letting the wound heal on its own.
  • Closing the wound with stitches.
  • Closing the wound with a skin flap or graft (borrowing tissue from surrounding skin).
  • A combination of the approaches listed above.
  • Involvement of another surgical specialist with unique skills (usually reserved for a larger than expected tumor)
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