Definition and Overview

Mohs micrographic surgery is considered one of the most effective techniques for treating skin cancer because of its preciseness. It involves carefully removing layers upon layers of skin tissue until all that is left is cancer-free skin.

The goals of Mohs surgery is to remove all traces of skin cancer and preserve as much of the healthy skin as possible to minimise the risks of surgery and to provide the best possible aesthetic results.

The procedure differs from regular skin excision in which the cancerous tissue is removed first then checked after for any remaining cancer. Doctors often do not know the extent of skin cancer and thus may remove even the healthy tissue or miss out on the rest of cancer cells. In Mohs surgery, patients will immediately know the spread of cancer since lab tests are performed during the procedure.

Depending on the extent or severity of cancer, it may take a few hours to an entire day to complete the procedure. Although it guarantees that the patient will leave the facility free of skin cancer, it does not provide an assurance against recurrences.

In the United States, it is expected that at least 1 in every 5 people will develop skin cancer. Although it is curable in the early stages, it can also become aggressive and lethal if patients fail to seek prompt treatment.

Who Should Undergo and Expected Results

This skin cancer surgery is effective on people who have been diagnosed with basal and squamous cell carcinoma. Basal cells are those found in the deeper layer of the skin. When they develop into cancer, they may appear as skin lesions. Squamous cells, on the other hand, are those that make up the upper layer of the skin (epidermis). They are also found in other parts of the body such as the eyes. When they become cancer, they often look like crusty or patchy lesions or nodules. While both of these are curable, squamous cell has the tendency to be aggressive and deadly when allowed to develop without medical intervention.

The procedure can be performed on skin cancer on the neck and head. It is also used in the ears, eyes, lips, hands, nose, and feet.

Mohs can also be helpful for patients with melanoma, which is considered as the most dangerous form of cancer because it is very difficult to treat once it has metastasized. At this point too, Mohs surgery may no longer be an effective treatment. Melanoma forms when cells known as melanocytes develop defective genes, which cause them to multiply abnormally and subsequently form tumours.

The surgery may also work on recurrent tumours, provided they grow on the same site. Doctors use it to treat recurrent skin cancers, especially those who have been previously diagnosed with basal and squamous cell carcinoma.

The procedure is not intended for people who have been diagnosed with blood disorders, those with skin infections and allergies, and who are severely sick and are not strong enough to undergo the procedure.

How Does the Procedure Work?

Often, Moh surgery is performed in an outpatient setting. However, since it is essential that the doctor has immediate and easy access to a lab that can microscopically study the tissue sample, it is usually carried out in a comprehensive health care facility like a large dermatology clinic or a hospital. Because the procedure may take a long time, it may be necessary for the patient to dedicate an entire day for it.

The procedure is performed by a Mohs surgeon. To become a Mohs surgeon, board certified dermatologists must complete a special training that exposes them to a wide variety of dermatologic surgical procedures and helps them gain the skills needed to accurately interpret skin histopathology.

Before the procedure, the doctor analyses the condition of the skin and determines whether the patient qualifies for Mohs surgery. If he is, the doctor proceeds with outlining the most visible carcinomas on the skin usually with the use of a pen. The area is then administered with local anaesthesia to minimise the pain. Sometimes the effectiveness of the anaesthesia wears off, particularly when the procedure is extensive. In such cases, re-administration is performed.

Using a sharp surgical tool such as a scalpel, the doctor slowly removes a layer of the cancerous skin along with a small margin tissue. This tissue is slightly larger than the actual tumour site and is used to determine the extent of skin cancer. The wound is covered with bandage while the removed sample is studied under a microscope. It may take at least an hour before the results come back.

The procedure is considered completed when all cancer cells have been removed. Otherwise, the surgery continues starting from the precise spot where the cancer cells have been found. The procedure goes on until there is no more sign of cancer on the tissue sample.

Possible Risks and Complications

One of the biggest risks of Mohs dermatology surgery is disfigurement especially when a large portion of the skin has to be removed. Such is the main concern for patients who have undergone Mohs surgery on nose or on any visible part of their body. This usually happens when cancer cells have already spread or have become aggressive. Thus, a common step undertaken after the surgery is the discussion of possible facial reconstruction or cosmetic surgery. A solution, for example after Mohs surgery nose, is skin grafting, wherein a healthy skin layer from another part of the body is transplanted into the wound site.

As much as possible, the doctor spares as much healthy skin as possible to minimise scarring, but scarring is a typical occurrence in Mohs surgery. While some of these Mohs surgery scars appear light or are easy to hide, some become keloids.

Bleeding may also develop during and after the procedure, and this includes haematoma, which may appear like a bruise. The patient can also expect soreness, pain, and tenderness in the surgical area. Hence, doctors may also provide medications to control these risks.

Infection is another issue, particularly since wounds create an entryway for pathogens to enter. Aside from pain relievers, doctors also often provide antibiotics.

In very rare cases, the procedure can lead to nerve damage.


  • National Cancer Institute: PDQ Skin Cancer Treatment. Bethesda, MD: National Cancer Institute. Date last modified July 20, 2012. Available at: Accessed August 19, 2013.

  • Upjohn E, Taylor RS.Mohs surgery. Rigel: Cancer of the Skin. 2nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 47.

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