Mohs surgery is an advanced surgical technique used for the treatment of skin cancers. The procedure offers the highest chance of cure from any treatment available, while conserving healthy tissue around the skin cancer. A Mohs surgeon is a qualified dermatologist who has undergone further sub-specialised training in pathology and surgery. The Australasian College of Dermatologists provides a list of accredited Mohs surgeons in Queensland.
In the early 1940s, Dr Frederick Mohs, Professor of Surgery at the University of Wisconsin, developed this treatment for skin cancer. Mohs surgery is a highly specialised treatment for the total removal of skin cancers. It is a sub-speciality of dermatology and your dermatologist has done further training registered with the Australian College of Dermatologists.
Mohs surgery is most commonly used to treat basal cell carcinomas (BCC) and intraepithelial carcinomas (IEC) or squamous cell carcinomas (SCC). It may also be used to treat a variety of other rarer tumours, including Microcystic Adnexal Carcinomas (MAC) and Extra-Mammary Pagets Disease (EMPD).
Mohs surgery involves excision of your skin cancer, with a margin of only 1mm, much less than the margin added with standard surgery. The tissue is then prepared by your surgeon for a technician, who makes microscope slides for your surgeon to assess. The Mohs technique is unique in that it achieves comprehensive analysis of all the margins around your tumour, both at the sides and underneath. Your surgeon is able to thoroughly assess all the edges to check that your skin cancer is fully removed. If tumour is still present at one or all of the edges, more skin is removed, from precisely where required and nowhere else. This is then also assessed under the microscope, to confirm complete removal. Each stage of surgery takes 1-2 hours. Once the skin cancer is removed, the hole in the skin is the surgically repaired.
Thus there are two main advantages of Mohs surgery. Firstly, the technique spares normal tissue that doesn’t need to be excised, and may be lost unnecessarily with a conventional surgical technique. This may well result in a smaller surgical defect that can be reconstructed with a smaller repair and scar, and achieve a superior cosmetic outcome. Secondly, the technique carries a higher cure rate than conventional surgery (99% vs 95%).
Very rarely, the skin cancer cannot be totally removed and further surgery or radiotherapy may be needed at a later date. In less than 1% of cases, perineural invasion is identified. This means the tumour has invaded the nerves in the area. In this setting, radiotherapy may be required after the surgery has healed.
For a number of reasons, the benefits of Mohs surgery are most applicable to tumours on the head and neck, or the digits. Mohs surgery is most commonly used for basal cell carcinomas. It is particularly useful in locations such as the nose, eyelid, eyebrows, lips and ears, where it is crucial to clear the skin cancer effectively whilst preserving all healthy tissue around it. Some types of basal cell carcinoma are particularly prone to being larger than they appear on the skin surface. These include micronodular and infiltrative, as well as recurrent tumours.
The surgical repair depends on the shape and depth of the defect, which is not known until the microscope slides have confirmed the tumour has been fully removed. The repair takes an average of 30 minutes, but may take longer for larger or more complex defects.
Tumours can sometimes prove significantly larger than apparent on the skin surface. The large defect that ensues may of course be confronting for patients. The reality is that it’s these patients who benefit most from the Mohs surgical technique. It is a big day, but the benefit comes in knowing that the tumour is all out at the end of it; and these patients have avoided the disappointment and challenges of receiving a likely result of ‘incomplete excision’ with standard surgery.
Once the tumour is fully removed, your Mohs surgeon will discuss the surgical repair with you. More local anaesthetic is injected at this time. Small defects may be repaired in a side-to-side fashion. The oval or circular shaped defect is converted to an ellipse shape, with small triangles of tissue removed from each end. Deep absorbable stitches are placed beneath the wound’s surface, and non-dissolving stitches are placed at the wound edges.
Defects in sites such as the nose and ears are often unable to be stitched side-to-side, due to the lack of loose skin in these locations. In this setting, there are three other options:
You will be asked to fast from midnight if you are undergoing collaborative surgery with a plastic or oculoplastic surgeon. Other patients should take a light breakfast prior to attending, and food and drink will be made available during the day.
Please take your medications as usual, unless otherwise directed. Most blood thinning medicines are continued, but please discuss these with your dermatologist. If you are on Warfarin, your INR should be checked two days prior to surgery, and you should contact Q Dermatology if your INR is above 3, as your surgery may need to be deferred.
Please use a chlorhexidine-based antibacterial body wash all over your body (avoiding your eyes) the day prior to surgery. This has been proven to reduce your chance of a wound infection following surgery. This can be purchased as 2% Microshield at most pharmacies.
The surgery is performed in an operating theatre at either Westside Private Hospital (Taringa) or North West Hospital (Everton Park). You should not drive yourself after the surgery. Relatives or friends cannot wait with you during the surgery, but will be advised when it is time to come to collect you.
Mohs surgery can take up to 4 hours, to ensure your cancer is completely removed. Expect to be at the hospital for at least several hours. It takes 1 – 2 hours to make the microscope slides after tissue is excised, so there is a wait between each surgical stage, and before the defect is repaired. You will wait in a recovery area during this time. Bring a good book, or alternative entertainment, with you.
You should arrange for at least 2 days off work (the day of treatment, and one day off afterwards) but may need longer, depending on the extent of your surgery. Please request a Medical Certificate in advance, if you need one.
Plan to avoid any strenuous activity that would cause you to sweat for at least 5 - 7 days. Avoid swimming for two weeks. Please contact us before your surgery day if you have any questions.
You will experience some discomfort after your surgery. This is generally easily managed with Paracetamol 1000mg, taken as needed up to 4 times daily. Your pain should steadily decrease in the 1 - 2 days after the procedure.
If you notice any blood seeping through your dressing, please lie down and apply pressure with clean gauze or tissues and your hand for 20 minutes. You will be given an after hours number to call if problems persist. If you have issues during the day please call Q Dermatology, and ask to speak to a member of our nursing staff.
Swelling is common following Mohs surgery, especially around the eyes, and lower cheek/neck area. Swelling may be decreased by sleeping with your head slightly elevated on 1 - 2 pillows, and by using an ice pack for short periods during the first 24 hours.
Any surgical wound may become infected. If your wound becomes red/sore/warm/tender or oozy, you should contact us to arrange prompt review.
Surgical sites are often numb, as the small nerve-endings in the skin have been severed or injured during the excision process. This numbness improves over months, but may be permanent.
All surgery results in a scar, with the aim being to achieve as fine a scar as possible. During the healing process, facial scars in particular are often red and bumpy. This is largely due to the inflammation that often forms around the dissolving stitches inside the wound. This settles over the course of approximately 12 weeks. You will be asked to keep your wound taped with a small piece of skin-coloured Micropore tape during this period, as there is evidence this improves healing. Some scars do, unfortunately, stretch over time or heal in a thickened fashion. Others develop telangiectasia (broken blood vessels), which is particularly common around the nose. These issues can be addressed with scar revision down the track, which may involve small surgical procedures, steroid injections, or lasers.
Sutures are typically removed in 4 – 10 days, depending on the site. You should call for review sooner if you have any concerns regarding your dressing or wound. A follow-up period of observation for at least 5 years is essential. Depending on your situation, your dermatologist may recommend that your follow-up occurs with them, or with your referring doctor, at 6 – 12 month intervals.
1. A Mohs surgeon is specially trained to fulfil all three roles:
Remove the cancerous tissue.
Read the histology (the pathologist), to confirm the cancer is fully removed.
Surgical repair of the wound.
2. The highest cure rates:
Mohs micrographic surgery is considered the most effective technique for treating the two most common types of skin cancer: basal cell carcinomas (BCCs) and squamous cell carcinomas (SCCs).
Up to 99% for a skin cancer that has not been treated before (highest cure rate).
Up to 94% for a skin cancer that has recurred after previous treatment (highest cure rate).
3. Precise results:
Mohs micrographic surgery examines 100% of cancer margins.
Spares healthy tissue.
Leaves the smallest scar possible.
4. Efficient, cost-effective treatment:
Single-visit day hospital surgery.
Lab work done on-site same day.