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Micrographic Surgery

What is Mohs?

Mohs micrographic surgery is a specialised surgical technique to remove skin cancers typically located on the central face. It was initially described by Dr Frederic Mohs, a general surgeon from Wisconsin in the United States in the 1930s.

The advantage of Mohs surgery over other forms of surgery is it allows preservation of as much healthy skin as possible while also offering the highest cure rate. Without Mohs , the surgeon has to take a much larger area of healthy skin around the cancer to ensure that it is fully removed. Despite this the cancer can still be incompletely removed and/or regrow at a later date leading to even more extensive surgery. Envisage a tree with roots. In order to remove all the roots a lot of ground has to be removed. With Mohs surgery only the tree and its roots are removed preserving all the healthy surrounding ground.

Mohs micrographic surgery is considered the ‘gold-standard’ treatment for certain types of skin cancer especially those on the nose, close to the eye, recurrent cancers, cancers that are large and cancers occurring in young people.

Mohs surgery allows 100% of the excised tissues margins to be assessed under microscope on the same day as your operation. If the area of skin removed shows any cancer remaining, you can have further surgery that same day to completely remove the cancer. In traditional surgery less than 1% of the tumour margin is assessed and this takes places days to weeks following the operation. By this point, if it shows that the cancer was not fully removed, the patient then needs to have far more extensive surgery.

During Mohs surgery the cancer is carefully marked out before being removed with a 2mm rim of normal skin. Dr Nelson then carefully scores the specimen to relax the edges of the excised skin down into the same plane as the base. This turns a 3-dimensional structure into a 2-dimensional structure. Once the sides and base of the excised skin has been fully ‘relaxed’ it is processed so the entire peripheral margin and the deep margin are visualised in a single plane using a high powered microscope. This allows for examination of 100% of the margin. Any cancer cells found are carefully mapped back to the patient. The patient is returned to the operating room. More anaesthetic is injected before a second stage is performed to precisely remove only the area of skin involved. This process is repeated until the entire cancer has been removed. You therefore keep as much healthy tissue as possible, which is so important for cosmetic reasons on your face and neck.

In conventional surgery a bread-loafing method is used to examine the cancer. The excised cancer is sliced up like a loaf of bread. Only a handful of slices will be assessed often days to weeks after the operation.

The huge advantages of Mohs surgery are reflected in the price. Mohs takes longer to perform but in Dr Nelson’s opinion if you are going to treat a skin cancer it is better to treat it properly first time rather than try to cut corners and end up with a bigger problem later on.

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