Mohs Micrographic surgery was originally developed by Dr. Frederic Mohs at the University of Wisconsin in 1930 to precisely identify and remove skin cancer while leaving healthy tissue surrounding the tumour intact. Mohs Micrographic Surgery has the highest percentage of cure rates compared to other methods (even if the tumour has been previously treated by other methods) – 98 percent or higher for the two most common types of skin cancer – Basal Cell Carcinomas and Squamous Cell Carcinomas.
Mohs Micrographic Surgery is a precise surgical technique used to treat skin cancer. During Mohs surgery, thin layers of cancer-containing skin are progressively removed and examined until only cancer-free tissue remains.
The goal of Mohs surgery is to remove all of the skin cancer while minimizing unnecessary removal of surrounding healthy tissue. By preserving as much healthy tissue as possible, we are able to reduce scarring and optimize reconstruction and appearance.
This technique allows for 100% evaluation of the tissue margins with results available within 60-90 minutes of processing. Mohs Micrographic Surgery is the gold standard of care, as it provides the highest cure rates possible - approximately 99% of skin cancers are cured through this technique.
The surgeon marks out the visible tumour and locally anesthetizes the tissue. Microscopic disease is usually present surrounding the visible tumour.
After the area is properly anesthetized, the visible tumour is excised using a scalpel technique and sent to the lab for processing using frozen sections. The wound is bandaged during processing.
The tissue is taken and sectioned into blocks and numbered. This is sent to the lab and completed using frozen sections. The tissue blocks are oriented and mapped. The tissue sample is stained and ready for microscopic evaluation. Each block of tissue is processed and analyzed separately
The surgeon analyzes the tissue under the microscope and documents the areas which are positive.
Only areas which have shown to be positive for skin cancer will be removed during a second stage of tissue removal. 1 – 2 mm of tissue are removed with each stage. This process (steps 1-5) is repeated until all the margins are cleared. On average, this usually takes two to three rounds of tissue removal.
Once all the skin cancer has been removed, the Mohs Surgeon will then assess the defect and discuss with the patient the options available for reconstruction, which depends on the size and location, and may include the wound healing on its own, rotation of skin tissue or a skin graft. In most cases, the reconstruction happens on the same day as the removal but on occasion, the Mohs Surgeon may refer to another specialist for more complex reconstructions.
Mohs Surgery offers the highest cure rate for the removal of practically any type of skin cancer. There are also many other effective treatments for skin cancer including cryotherapy, surgical excision, scraping and burning of the tumour or laser therapy. Each one of these therapies requires the Surgeon to estimate how wide of a margin to treat or remove around the tumour. Some of the advantages to using the Mohs Micrographic Surgery procedure over other skin cancer treatments including its high cure rates. Mohs Micrographic Surgery is indicated when:
· The tumour is in a cosmetically sensitive area where preserving as much normal tissue
as possible is important to maintain the function and appearance
· The tumour has recurred after previous treatment
· Are large
· The tumour is growing quickly
· The tumour’s edges are very ill-defined and hard to decipher
· Are located in scar tissue
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