Mohs Surgery

Mohs surgery is a highly specialized technique in dermatologic surgery for treating skin cancer. The procedure is named for Frederick E. Mohs, the surgeon who developed the technique, and is also known as Mohs micrographic surgery. Since its development, Mohs surgery has been refined into the most precise and advanced treatment for skin cancer, yielding success rates up to 99 percent. Mohs surgery is so effective because 100 percent of the surgical margins are evaluated, compared with less than 5 percent by traditional techniques.

During this procedure, the surgeon removes thin layers of skin one layer at a time and examines each layer under a microscope to determine if any cancer remains. This procedure continues until the tissue is cancer-free. A fellowship-trained Mohs surgeon is specially educated in the reading of these slides and can map microscopic findings to the surgical site.

What You Need to Know

  • The goal of this treatment is to minimize the chance of the cancer growing back, preserve as much healthy skin as possible and maximize the functional and cosmetic outcome.
  • Mohs surgery is performed under local anesthesia on an outpatient basis, and the entire procedure usually lasts several hours.
  • Depending on the extent of the cancer, reconstructive surgery may be necessary and can often be performed on the same day by your Mohs surgeon.
  • Mohs surgery is the standard of care for early stage basal cell carcinomas and squamous cell carcinomas of the head and neck, as well as other rare skin cancers.
  • It is important to choose a fellowship-trained Mohs surgeon who is a member of the American College of Mohs Surgery.

Why is Mohs surgery performed?

Mohs surgery commonly addresses skin cancer that:

  • Is located on any sensitive area where it is important to minimize the removal of normal healthy tissue, such as the head and neck, fingers, toes or genitals

  • Is of an aggressive subtype (e.g., infiltrating basal cell carcinoma)

  • Develops in patients with suppressed immune systems (e.g., organ transplants and lymphoma)

  • Was previously treated and has come back

  • Is growing quickly

  • Is large


The Mohs procedure takes place in the office setting with the surgeon using a local anesthetic to numb the area completely. After local anesthesia has been injected, the surgeon uses a scalpel to remove thin layers of skin one layer at a time in a saucer shape, which are then marked with colored dyes and mapped. Some cancers may be more deeply rooted in lower levels of the skin, appearing small on the surface but with extensive growth several skin layers below. Other cancers may be shallow and require only a small excision of the surface area.

Over the next hour, the specimen is frozen, sliced into very thin sections and processed onto glass slides by a Mohs histotechnician. The Mohs surgeon then examines the slides under the microscope to gauge the extent of the skin cancer and identify microscopic roots. If tumor cells remain at any of the margins, the map is used to remove an additional tissue layer precisely at the area where cancer remains. This procedure continues until the tissue is cancer-free and allows normal, healthy, surrounding tissue to be spared.

After the skin cancer has been removed by Mohs surgery, repairing the site of the skin cancer using reconstructive surgery can often be performed by your Mohs surgeon on the same day.

Care After Mohs Surgery

The surgeon will dress the wound and provide care instructions. This may include a topical ointment, medication or special care instructions to reduce the risk of infection.

Reconstruction After Mohs Surgery

In the majority of cases, reconstructive surgery will be performed by your Mohs surgeon immediately after the skin cancer has been removed. Large defects in cosmetically and functionally sensitive structures such as the nose or the areas around the eyes or ears may require a skin graft or local flap to restore the features of the face. Other Mohs procedures may not require reconstructive surgery at all. In advanced cases requiring larger reconstructions that are better performed in the operating room under sedation or general anesthesia, your Mohs surgeon may coordinate your reconstructive work with a highly qualified Johns Hopkins plastics, facial plastics or oculoplastic surgeon. A consultation with your Mohs surgeon will help determine what type of reconstructive surgery you will need.

Reconstruction After Mohs Surgery | Amber's Story

Mohs surgery for the removal of squamous cell carcinoma left Amber with a large wound on her face. Willing to travel anywhere for the best facial plastic and reconstruction surgeon, Amber found Lisa Ishii, M.D., at Johns Hopkins to repair her cheek and is delighted with the outcome.

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