Mohs surgery

One of the most advanced treatments for skin cancer is named after the man who invented it in the 1930s, Dr Frederick Mohs. In Mohs' surgery, the tumour is removed piece by piece. Each piece is immediately frozen and examined under a microscope. If some cancer might still be present, more tissue is removed and examined. This goes on until there are no signs of any cancer cells. Reconstruction is then carried out.

Mohs Micrographic Surgery (MMS) relies on the surgeon also being a pathologist and identifying cancer cells. The surgery is very precise and means that the maximum amount of healthy tissue is retained, while removing cells that could cause a recurrence of the cancer.

The cure rate for MMS is up to 99 per cent for skin cancers that have not been treated by other methods and more than 90 per cent where other forms of treatment have failed.

Some tumours do not respond to common treatments, including those greater than 2cm in diameter, those in difficult locations, such as the eyelid, and tumours complicated by previous treatment. Removing a recurring skin cancer is more complicated because scar tissue makes it difficult to differentiate between cancerous and healthy tissue. Again, the Mohs approach makes effective treatment possible.

Mr Malhotra recommends MMS to treat difficult basal cell carcinomas (BCC), and squamous cell carcinomas (SCC). Both are most often caused by excessive exposure to UV light from the sun or sun beds.

It can also be used to treat less common tumours, including melanoma, sebaceous carcinoma (SG) or microcystic adnexal carcinoma (MAC) — a tumour of a facial sweat gland. These may require more than one visit as often the skin pieces need to be processed as paraffin sections, which takes considerably longer, in order to provide greater clarity.

MMS is particularly useful when:

A cancer has been treated previously and recurred.
Scar tissue exists in the area of the cancer.
The cancer is in an area where it is important to preserve healthy tissue for a most functional and cosmetic result, such as eyelids, nose, ears, lips.
The cancer is large.
The edges of the cancer cannot be clearly defined.
The cancer grows rapidly or uncontrollably.

What to expect

You will generally be under local anaesthesia as a day surgery case.
The surgeon removes the first layers of skin cancer and you return to the waiting area with a pad over your eye. You may need to wait an hour or so and may want to bring something to read.
The surgeon traces the path of the tumour using his map of the surgical site (a drawing of the removed tissue that is used as a guide to the precise location of any remaining cancer cells) and a microscope.
If any of the sections of skin contain cancer cells, you will return to the treatment room. Another thin layer of tissue is removed and examined for cancerous cells while you return to the waiting area.
Occasionally, top-up anaesthetic injections are needed before the repeat excisions.
The process continues layer by layer until the cancer is completely gone.
In most cases, complete excision is achieved within two excisions (often called levels), although three or four levels may be needed in difficult cases. As much healthy tissue is kept as possible.
Mr Malhotra will decide on the best method of reconstruction once the cancer is completely removed.
Reconstruction is carried out either immediately after MMS or within a week.

All procedures begin with a consultation. For full information about what to do before and after surgery, see Patient information.

Mohs surgery

What to expect

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