What is Mohs surgery?
Mohs Micrographic Surgery is a precision surgical technique for the treatment of skin cancer.
International skin cancer guidelines recommend Mohs surgery as first line treatment and gold standard for skin cancers at high risk for recurrence and in cosmetically sensitive and/or functionally important areas.
It has been proven to provide the highest cure rates (99%), being the most cost-effective and associated with best cosmetic outcomes when treating skin cancer.
With this technique, performed in most cases under local anaesthetic in a day theatre, the tumour is removed with a thin layer of surrounding healthy tissue. The removed tissue is then processed immediately by the Mohs surgeon in a Mohs histological laboratory on site, while the patient returns to the ward.
The Mohs specific method of processing allows tissue slides to be produced that show the whole, 100% complete cut surface around and underneath the tumour.
These slides are then examined by the Mohs surgeon and will show very accurately any remaining tumour.
If residual tumour is detected, the patient then returns to the day theatre for further excision, but only on the area of remaining tumour, leaving the healthy tumour-free part of the wound alone. This allows for the smallest possible defect when removing the skin cancer.
As soon as the Mohs surgeon confirms the skin cancer to be completely removed, a specialist reconstructive surgeon or the Mohs surgeon repairs the defect where the cancer was removed.
The result of Mohs surgery is the highest possible cure rate, with the smallest possible defect, making closure of the wound potentially simpler.
Dr de Wet offers Mohs surgery to suitable candidates in Stellenbosch, Somerset West and greater Cape Town area. He is a fellowship trained Mohs surgeon and forms part of the Skinmatters Mohs and Reconstructive Unit.
How does mohs surgery differ from traditional skin cancer surgery?
In comparison, traditional surgery will remove the cancer with a wide margin (>5mm for high-risk BCC’s and >10mm for SSC’s) leading to larger defects and more complicated reconstructions.
The technique is also essentially “blind”, meaning tumour can be left behind, despite sacrificing a wide rim of healthy tissue.
The histological assessment that follows standard excision involves random vertical sectioning. With this technique only 1% of the surgical margin will be assessed (comparing to 100% with Mohs Surgery). Therefore tumour can be missed and left behind.
An improvement on the standard excision technique is to have a pathologist on hand in theatre to perform a few random vertical frozen sections while the patient is on the table. Again, the whole cut surface is not evaluated but random areas only (< 1% of the margin), therefore tumour can still be left behind.
What to expect on the day of surgery:
- During your initial consultation the surgery will be discussed in detail.
- Plan to spend the whole day with us.
- The morning will be dedicated to the excision of the tumour and the analysis of the tissue.
- The excision will be done under local anaesthetic.
- The reconstruction of the defect will only take place in the afternoon once it has been confirmed that the skin cancer is completely removed.
- This is typically done under conscious sedation.
- Instructions will be given to you by the reconstructive team regarding wound care and follow-up.
