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Mohs Surgery

What is Mohs Surgery?

Mohs surgery is the gold-standard technique for the removal of skin cancers including basal cell cancers (BCC) and squamous cell cancers (SCC). It was developed in the 1930s by Dr. Frederic Mohs.

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The goal of Mohs surgery is to remove the skin cancer completely, while preserving as much healthy tissue as possible. The highly specialised technique allow the surgeon to see where the cancer stops i.e they can examine 100% of the skin cancer margins, compared to only 1% of the margins typically seen with standard surgery (local excision).

Close-up shot of microscope with metal lens at laboratory..jpg

Who can perform it?

Mohs surgeons are specialist dermatologists who have undergone additional fellowship training in Mohs surgery. This training includes examination of skin cancers under the microscope, tracking and excising the roots of skin cancers and repairing the area where the cancer was surgically removed.

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When is it recommended?

Mohs surgery is the best treatment for skin cancers: 

  • On the face including around the eyes, ears, nose, mouth

  • On the fingers, hands, lower legs, feet and genitals

  • Recurring after previous treatment

  • With borders that are hard to define 

  • That are large or aggressive 

  • That are rare types e.g. sebaceous carcinoma

What does the procedure involve?

  • The surgery is typically conducted in a day surgery unit.

  • Your specialist carefully marks the area where the skin cancer is and numbs the area with a local anaesthetic.

  • The visible portion of the skin cancer along with a thin margin of normal tissue is removed using a scalpel. 

  • A temporary bandage is placed on your wound.

  • The cancer is carefully dyed, orientated then frozen and processed in an on-site laboratory. 

  • Microscope slides are made with the removed skin cancer tissue.1 This process can take 1-2 hours.

  • Your specialist then checks the microscope slides for any remaining cancer cells along the edges of the tissue.1

  • Should any roots remain, the process is repeated with additional layers (or stages) taken until all the cancer is cleared. For most people the procedure takes just a few hours but there is a very small chance that it could take all day.2

  • After the cancer has been completely removed, your wound can be left to heal on its own or repaired; depending on the extent of the procedure.2

  • Types of repairs include:2

  • Side-to-side closure – using stitches to close the wound 

  • Skin graft – using skin graft from another part of the body to cover the wound

  • Skin flap – shifting skin from an adjacent area to cover the wound  

How does Mohs surgery differ to standard surgery?

Standard surgery involves removing the visible cancer and a small margin of surrounding healthy tissue all at once.2 It relies on the surgeon being able to see the extent of the cancer to determine a safety margin to cure the cancer. However, basal and squamous cell cancers often have invisible roots that cannot be seen by the naked eye. 

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Standard surgery may estimate a larger safety margin than is required to cure the cancer, resulting in a larger scar with too much healthy tissue being removed. Conversely, too little tissue may be removed, leaving roots in place and increasing the chance of the cancer recurring. 

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Mohs surgery maximises the chance of complete cure of the cancer and minimises the need for more difficult revision surgery should the cancer return. 

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The main disadvantage with Mohs is the length of time the procedure can take, as each layer must be individually analysed. This takes longer than traditional cancer excisions. However, in most cases it is worth spending the extra time to be certain the entire cancer has been removed. It allows surgeons to verify that all cancer cells have been removed at the time of surgery. Mohs surgery may be associated with higher costs. 

When should I have surgery?

It is important to get any skin cancer treated at the earliest possible time to help minimise the size of the scar and the complexity of the surgery. The longer a tumour is left, the greater the risk of invasion. 

What would happen if I left my cancer untreated?

If untreated, the cancer will continue to grow beneath the surface of the skin. It may grow into nerves and blood vessels, and cause pain. It may break the surface of the skin and form an ulcer. 

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Basal cell cancers are also known as “rodent ulcers” because if untreated they become larger and may develop deep roots, eating away at skin, nerves and underlying tissues (including cartilage, bone and eye tissue) requiring more complex surgery to remove and reconstruct the wound left behind. It is extremely rare for basal cell cancers to spread to the rest of the body. 

Squamous cell cancers, however, can spread to the body and may be fatal if left untreated. 

Do I still need surgery if my biopsy area appears to have healed?

Most skin cancers have invisible roots beneath the surface of the skin which are not seen by the naked eye. In most cases, your biopsy was performed to provide information about the spot, but not to treat it. 

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The surface of the wound may have healed but beneath the surface, roots remain. By the time the skin cancer grows back from its roots and becomes obvious on the surface, deeper invasion may have occurred. 

Where can I get more information?

 

 

Please visit The Australasian College of Dermatologists’ website.

 

 Mohs Surgery: https://www.dermcoll.edu.au/atoz/mohs-surgery/

Find a Mohs Specialist: https://www.dermcoll.edu.au/find-a-derm/find-a-mohs-specialist/

References 

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