What is skin cancer?
Skin cancer is by far the most common malignant tumour in humans. The most common types of skin cancer are basal cell carcinoma, squamous cell carcinoma and melanoma. Both basal cell carcinoma and squamous cell carcinoma begin as a single point in the upper layers of the skin and slowly enlarge, both along the surface and downward. These extensions cannot always be seen directly. The tumour often extends far beyond what is visible on the surface of the skin. Basal cell carcinoma metastasis (spread) is extremely rare, and usually only occurs in the setting of long-standing, large tumours. Squamous cell carcinoma is slightly more dangerous and patients must be observed for any spread of the tumour. Such spread is still infrequent.
Figure 1 – depicts skin cancer where a vertical cut has been taken, which would be interpreted as clearance of the tumour (a), but one can see that if the cut had been made in another site where the tumour did extend to the margin (b), the result would have been a positive. Hence because of the random intermittent section of tissue, inevitably tumour can be present at excision margins without detection.
What is Mohs Surgery?
Mohs surgery, a technique for the microscopically- controlled excision of skin cancer, produces the highest cure rate for non-melanoma skin cancers suitable for the procedure – FIGURE 2.
The technique combines surgical removal of the skin cancer in a precise layer-by layer removal, with immediate microscopic examination of the removed tissue, using horizontal frozen sections to ensure no tumour remains.
Once clearance is achieved, the wound can be repaired. This process should not be confused with frozen sections, which refers to random, intermittent sectioning, examining only a small area of the overall specimen.
The Mohs Procedure
The sequence of events is depicted in FIGURE 2 and the basics of the method are pictured in FIGURE 3.
1 - 4 Following local anaesthesia, the lesion is debulked with a curette. A 2 – 3mm margin of normal appearing skin is outlined around the remaining tumour as it appears on the skin surface. The lesion is surgically removed, producing a saucer-shaped specimen. This shape is critical to the later preparation of a complete survey of the excision margins, which cannot be achieved by any other method.
The removed tissue is then divided into segments and colour-coded to orientate each specimen and marked on a detailed diagram.
5 – 6 The tissue is frozen on a cryostat. The under-surface and all edges of each section are then microscopically examined for evidence of remaining cancer.
7 If any microscopic roots of the cancer are present, the residual tumour is located by way of the map, which then allows for removal from any area in which tumour still persists.
8 - 9 This process continues in a layer-by-layer fashion until microscopically controlled tumour extirpation has occurred.
Reconstruction can then be performed immediately or as a planned procedure.
Who is suitable?
Patients with basal cell, squamous cell carcinoma and certain rare neoplasms should ideally be treated by
this technique if they fall within one of the following criteria:
- Recurrent skin cancer.
- Skin cancers occurring in sites where recurrence rates with traditional approaches are high. Such areas include tumours around the eye, nose and lips.
- Incomplete removal of tumour.
- Large tumours (greater than 2cm in diameter).
- Tumors with indistinct skin margins.
The main advantages are related to the meticulous methodology of tissue preparation and microscopic examination by the Mohs surgeon. The advantages of Mohs surgery include:
- The highest cure rate.
- Minimal removal of normal, tumour-free tissue.
- Performed under local anaesthesia as an outpatient, although general anaesthesia facilities are available if required.
- Reconstructive surgery takes place under optimum conditions (tumour-free). Because Mohs surgeons are also dermatologists and have training in reconstructive surgery, they have extensive knowledge of the skin and its healing properties, which helps produce the best cosmetic result.
- Procedure is usually completed within half a day
Each patient is unique… however, there are some common risks.
The exact size of the final defect, following clearance, cannot be predicted prior to surgery. The tumour may be much larger than estimated from the surface appearance.
A scar will remain at the site of removal. Every effort is made to obtain optimum cosmetic results, but the primary goal is always to remove the entire tumour.
As a patient, you should understand there is no absolute guarantee that any procedure will be totally free of complications or adverse reactions.
There may be loss of motor (muscle) or sensory (feeling) nerve function. In the rare instance where tumour involves nerve fibres, the nerves must be removed along with the tumour. If a sensory nerve is injured or removed, numbness results. Sensation will usually, but not always, return. If a motor nerve is involved, the patient may be unable to move the muscle that the nerve served. In some, but not all cases, this nerve function will return after a long period. Rarely, a few patients experience intermittent shooting pain at the surgical area. However, this is a very unusual complication.
The tumour may involve an important structure. Because tumours often occur in the head and neck, many are near or on vital structures such as the eyes, nose or lips. In such cases, portions of these structures may have to be removed with resulting cosmetic or functional deformities.
The surgical area may remain tender for several weeks or months after surgery, especially if large amounts of tissue were removed.
Skin grafts and flaps used to cover surgical areas may occasionally not survive.
What’s the next step?
If you already have an appointment booked at The Skin Specialist Centre, you can easily add a skin cancer treatment consultation to your booking by calling our friendly team on (09) 524 5011. If you have never been to The Skin Specialist Centre, you can either give us a call on (09) 524 5011 or make an enquiry by clicking on the Enquire Now option below.