What is Mohs Micrographic Surgery?
Mohs Micrographic Surgery is a highly specialised technique for treating skin cancers including basal cell carcinomas (rodent ulcers; BCCs) and squamous cell carcinomas (SCCs).
This is a procedure carried out in stages, which removes all cancerous cells with the highest cure rate of about 99%. It also spares normal tissue leaving behind a smaller scar and therefore a better cosmetic result.
A Mohs surgeon will have learned to remove the cancerous cells in a specific way by beveling the incision at the correct angle which enables fresh frozen horizontal sectioning and examination of the full tumour margin. The surgeon will be able to analyse the specimen under the microscope and determine whether the cancer is clear. If there is any residual cancer, the site can be pinpointed and further tissue removed for analysis.
Advantages of Mohs surgery:
- The procedure enables examination of 100% of tumour margins - this provides the highest accuracy and best cure rates.
- This is most important on high risk sites such as the nose and near the lips or the eyes.
- Some types of skin cancer have more extensive roots which are invisible. Standard excision might miss these roots leaving behind the skin cancer.
- Sparing of healthy tissue - the tissue can be removed with a smaller amount of your normal tissue, meaning that the scar is ultimately reduced and the cosmetic appearance is better.
The procedure
- The whole procedure is typically undertaken in one visit but it is worth being prepared to stay for the full day. Occasionally you will need to return the next day for the reconstruction.
- As the patient you will attend in the department at the beginning of the day and the first layer will be taken under local anaesthetic. Once this has been taken, a bandage will be applied and you will wait in a separate private waiting area until the sample has been analysed.
- The tissue sample will then be stained by the surgeon to orientate it, frozen using a device called a cryostat and then cut into horizontal sections by a biomedical scientist. These will then be pressed down on to slides and stained for histological analysis. When these are ready (typically 1-2 hours), the surgeon will read the slides and inform you whether you need any layers to remove the cancer.
- This process continues until the tumour is completely removed.
- Once you are informed the tumour is removed, the Mohs surgeon will discuss the defect and options for how it will be closed. Depending on the site and size of the defect, the options might include leaving the defect to heal up from the base (secondary intention), closing it together directly (primary intention), taking a skin graft from somewhere else on your body which best matches the defect or performing a flap (moving skin locally into the defect).