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Skin Cancer and Mohs Surgery

After our last blog you may have had a skin check! Although it is a chilly day for late October the NIWA alert for today recommends sun protection from 9.30 am to 4.30 pm. A cold day does not necessarily mean that no sun protection is needed!

Basal cell skin cancer is the most common form of skin cancer in New Zealand. These skin cancers are fully curable once they are completely removed. They are different from melanomas.

There are lots of ways to treat a basal cell skin cancer. It is important that the correct type of treatment is applied to the basal cell cancer depending on where it is on the body. The highest cure rate is getting it cut out with surgery. The other ways to treat them include freezing with liquid nitrogen, using a cream called imiquimod and a technique called curettage and cautery which involves scraping away the skin cancer with a special spoon shaped instrument and then cauterising the base.

Not all basal cell skin cancers are exactly the same when they are examined under the microscope. Some are more invasive than others which means they can spread further within the skin than can be seen with the naked eye. This can be a problem for surgery especially on the face, for example around the eyes and nose, as it may be impossible to know where they stop and start. 

A choice of treatment your dermatologist may recommend for some difficult basal cell skin cancers is called Mohs surgery. Skin cancers grow in a higgledy-piggledly way. Some of the “roots” may be longer than others and growing in lots of different directions. Frederic Mohs was an American surgeon who invented this technique. The technique involves carefully following the “roots” of the skin cancer until it is fully removed by examining the cut out skin cancer under a microscope during the operation and then returning to the exact location where the cancer remains if more needs to be removed. Mohs is usually done with a local anaesthetic and not general anaesthetic. For some this may mean re-entering the operating theatre several times during the day until the dermatologist is certain it has all gone. Once the skin cancer has been completely removed the hole that has been made by the surgery will be repaired.

Mohs surgery has an advantage that it only removes the exact amount of skin that is needed to get rid of the skin cancer and no more. Mohs surgery keeps the hole as small as possible and therefore the smallest scar so that the best possible cosmetic outcome can be obtained. Mohs has a high cure rate for difficult basal cell skin cancers. Five years after a Mohs operation for difficult basal cell skin cancers that have never had previous treatment, there is an approximate 98-99% cure rate and for those difficult basal cell skin cancers that have come back after a standard surgery, there is an approximate 95% cure rate.

The NZDSI has recently formed the New Zealand Society of Mohs Surgeons to promote the highest standard of Mohs surgery. The New Zealand standards adopted are intentionally equivalent to those of The Australasian College of Dermatologists which represents all Australian dermatologists. NZDSI approved Mohs surgeons have to complete additional mandatory continuous professional education to maintain their Mohs skills as this is a specialised technique not performed by all dermatologists. You can find more details about Mohs surgery and a list of NZDSI approved Mohs surgeons in this website.