Mohs Micrographic Surgery

What is Mohs micrographic surgery?

Mohs micrographic surgery is a specialist method of removing skin cancer, first devised in the 1930s by Dr Frederic Mohs. The cancer is taken off in thin layers, each examined under the microscope that same day so that every edge of the removed tissue can be checked carefully. If any cancer is seen at an edge, the surgeon removes a further layer only from that precise area. This is repeated until the edges are clear.

This approach gives the highest chance of removing all of the cancer in one day, while removing as little healthy skin as possible. Mohs surgery is carried out by specially trained Mohs surgeons, and Dr Mounsey can refer you to a Mohs surgeon colleague when it is the most appropriate option.

What is it used for?

Mohs surgery is most often used for basal cell carcinomas, and sometimes for squamous cell carcinomas and some rarer skin cancers. It is usually recommended for skin cancers on the head and neck, particularly in areas where preserving healthy tissue is important, such as around the eyes, nose, ears and lips; for skin cancers with poorly defined edges or an aggressive growth pattern; for large skin cancers; and for skin cancers that have come back after previous treatment.

Many skin cancers can be treated just as well with a standard excision, which usually has a shorter waiting time. Your dermatologist will discuss which option is best for you.

Before your procedure

You will usually have a consultation with the Mohs surgeon beforehand to discuss the procedure, the likely size of the wound and the options for repairing it. If you have private medical insurance, please contact your insurer to obtain pre-authorisation before booking.

Please tell the surgical team about any medicines that thin the blood, any pacemaker or other implanted device, and any allergies. You can eat and drink normally on the day. Plan to spend most of the day at the clinic, bring something to read and any regular medicines, and arrange for someone to take you home, as you may not be able to drive, particularly if the surgery is near your eye. If you smoke, stopping for two weeks before and after surgery helps the wound heal.

What happens on the day?

The surgery is carried out under local anaesthetic, so you are awake throughout. The surgeon marks the area, injects the local anaesthetic and removes the visible cancer with a thin layer of surrounding skin. A temporary dressing is applied, and you wait in a recovery area while the tissue is processed and examined under the microscope, which can take up to a few hours.

If any cancer remains at an edge, you return for another layer to be removed from that area only. In around 90 in 100 cases, the cancer is cleared after one or two stages, though some people need more. Because of the waiting time between stages, the whole process can take most of the day.

What to expect afterwards

Once the cancer has been completely removed, the wound is repaired. Depending on its size and site, it may be left to heal naturally under a dressing, which can take several weeks to two months; closed with stitches; or repaired with a skin graft or skin flap, in which nearby skin is moved to cover the wound. Occasionally, the repair is carried out by another specialist surgeon on a different day.

Some swelling and bruising are common, particularly around the eyes. The wound usually heals within a few weeks, and the scar continues to improve for up to 18 months.

Aftercare

Keep the dressing in place and dry for at least 48 hours before showering, unless you are advised otherwise. Rest for the remainder of the day and avoid bending, heavy lifting and strenuous activity for at least a week. Sleeping with an extra pillow can help reduce swelling after surgery on the face. Stitches are usually removed after 7 to 10 days, and your surgical team will arrange any dressing changes.

If the wound bleeds, press firmly on it with a clean, folded cloth or gauze for 10 to 15 minutes without lifting to check. If it is still bleeding after a second period of firm pressure, seek medical advice.

Paracetamol can be taken for discomfort once the local anaesthetic wears off. Avoid aspirin and anti-inflammatory painkillers such as ibuprofen for the first couple of days unless they have been prescribed for you, as they can increase bleeding. Avoiding alcohol for 48 hours and not smoking or vaping while the wound heals both help healing.

Contact the clinic if you notice signs of infection, such as increasing pain, redness, warmth or swelling around the wound, pus, or a fever, or if you have any other concerns.

Once the wound has fully healed, protect the scar from the sun with a broad-spectrum sunscreen of SPF 30 or above for at least six months, as sun exposure can darken or redden a new scar.

What are the risks?

Common side effects are pain, bleeding, bruising, swelling and scarring. Less common risks include infection, a collection of blood under the wound, wound opening, failure of part of a graft or flap, and nerve damage, which can cause numbness or, rarely, weakness of the facial muscles. Recurrence after Mohs surgery is uncommon, usually a few in 100 over several years, and less likely than after standard surgery.

Results and follow-up

As the margins are checked while you wait, you will normally know before you leave that the cancer has been cleared. Follow-up appointments will be arranged for wound checks and stitch removal, and your dermatologist will advise on longer-term skin checks. Anyone who has had a skin cancer has a higher chance of developing another, so regular self-examination and sun protection remain important.

More information

British Association of Dermatologists patient leaflet: https://www.bad.org.uk/pils/mohs-micrographic-surgery

This page gives general information only and is not a substitute for a consultation. Everyone's skin is different, and what is right for you will depend on your own circumstances. If you are worried about a skin problem, please book an appointment with Dr Mounsey or speak to your GP. If you have a mole or skin lesion that is changing, bleeding or growing quickly, please seek medical advice promptly.