Mohs micrographic surgery involves surgical excision of cancer-containing tissues and systematic microscopic examination of all cut surfaces. It is a highly specialized procedure for the total removal of skin cancers.

Unlike most surgical cancer removals, Mohs uses frozen sections stained with dyes to help identify different skin edges. The freezing process allows for an immediate examination.


This method involves five separate steps:

  1. Removal of the bulk of the cancer with a skin scraper (a curette).
  2. Surgical removal of a thin layer of skin.
  3. Drawing a map and preparing stained frozen tissue sections.
  4. Examination of the excised tissue under the microscope. After the tissue is removed, it is marked with colored dyes to distinguish the different skin edges.
  5. The entire procedure (except step 1) is repeated but only in the area of the remaining cancer. Only by careful, systematic microscopic examination of the removed skin can one be as certain as possible that no cancer remains.

During Mohs micrographic surgery, the tissue is examined in a different and more thorough manner than is normally performed by a pathologist associated with an operating room. Mohs micrographic surgery examines the entire sides and undersurface of the excised tissue. If one looks at a loaf of bread, Mohs micrographic surgery examines the whole crust rather than a few slices of the loaf.


How long does Mohs micrographic surgery take?

Total removal of a skin cancer, which may involve several surgical stages, is usually completed in one day. After the surgery, a decision is made as to the best way to manage the wound created by the surgery.

How effective is Mohs micrographic surgery?

Using the Mohs micrographic surgical technique, the percentage of success is very high, often 95% to 99%, even if other forms of treatment have failed. Therefore, with this technique, an excellent chance of cure is achieved. However, no one can guarantee a 100% chance of cure.

Will the surgery leave a scar?

Yes. Most forms of therapy will leave a scar. However, the Mohs micrographic surgical procedure tends to minimize this as much as possible. After the wound is healed, you may wish to have the scar improved. Generally, time alone will improve all scars.

What are the advantages of Mohs micrographic surgery?

After the initial tissue is removed, the surgeon can pinpoint with the microscope the areas where there is cancer and then selectively remove tissue only from those areas in the following surgical stages. In this way, the skin cancer is traced out to its roots with little guesswork involved, which results in:

  1. The removal of as little normal tissue as possible.
  2. The highest chance of curing the patient (under certain circumstances).

What are the disadvantages?

Mohs micrographic surgery is a process that may involve several surgical stages. The time for this procedure may take several hours and often all day.

What’s the next step after Mohs micrographic surgery?

When we have determined that the skin cancer has been completely removed, a decision is made about what to do with the wound created by the surgery. Usually, there are two choices:

  1. To let the wound heal by itself (granulation).
  2. To repair (close) the wound with stitches (either by bringing the wound edges together, or with a skin flap or skin graft).

What happens if I do not have my skin cancer treated?

All types of skin cancer will grow and invade nearby tissue. How fast a skin cancer will grow is unpredictable and varies from person to person. Sometimes skin cancer will destroy important structures such as the nose, lip or eye. Occasionally, skin cancers can be life threatening.



Cancer is tissue which grows at an uncontrollable and unpredictable rate. In the skin, there are three main forms: basal cell carcinoma, squamous cell carcinoma and malignant melanoma. The names refer to the cell types in the top skin layer (the epidermis) from which these cancers are derived.

The most common types of skin cancers are basal cell carcinoma and squamous cell carcinoma. If not removed completely, basal cell carcinoma and squamous cell carcinoma can enlarge from the point where they first occur, and can invade and destroy structures in their path. Basal cell carcinoma is unlikely to spread to distant parts of the body (metastasize). However, some squamous cell carcinomas can metastasize. These types of skin cancers are generally recognized in their early stages and are therefore easily cured.

Malignant melanoma, on the other hand, may be life threatening if not treated early. It usually appears as a brownish-black spot or bump on the skin which enlarges and sometimes bleeds. Sometimes melanomas arise in moles which have been present for many years.