Overview

Mohs micrographic surgery is a special type of surgery used to remove skin cancer. It’s often called Mohs surgery or MMS for short.

Mohs surgery aims to remove all the cancer cells in your skin while leaving as much healthy tissue as possible.

We do this by removing one layer of tissue at a time. Each time we remove a layer, we examine it under a microscope. If that layer contains cancer cells, we remove another layer. We repeat this until there are no more cancer cells.

Watch our ‘Mohs surgery explained’ video on YouTube to learn more.

Slow Mohs compared to standard Mohs surgery

Slow Mohs surgery uses a slower method for examining each layer of skin tissue than standard Mohs surgery. This allows us to treat more complex cancers. The whole procedure can take several days and you’ll need to make multiple trips to the hospital.

Your doctor might have recommended slow Mohs surgery for you because you have:

• dermatofibrosarcoma protuberans (DFSP)
• lentigo maligna (LM)
• a complex diagnosis
• an infectious disease, such as HIV or hepatitis

Benefits of Mohs surgery

In other methods for removing skin tumours, it’s more difficult for your surgeon to know where the tumour starts and ends. This can lead to a bigger wound and scar if too much healthy tissue is removed. There’s also a chance that your surgeon does not remove enough of the tumour, leading to the cancer coming back.

Mohs surgery is the most effective way of making sure we remove all the cancer cells in your skin while keeping as much healthy skin as possible.

It’s best to treat skin cancer quickly. If we do not remove it, it will continue to grow, which means you might need more aggressive treatment later.

Risks of Mohs surgery

Like all surgeries, Mohs surgery has some risks. Your doctor will explain the risks to you and answer any questions you have.

The risks include:

• bleeding in the area we do the surgery
• pain after surgery
• temporary or permanent nerve damage that leads to numb skin
• infection
• scarring

Your surgeon will minimise these risks as much as possible. Talk to us if you have any concerns.

Giving your permission (consent)

We want to involve you in decisions about your care and treatment. If you decide to have the procedure or treatment, we’ll ask you to sign a consent form. This says that you understand what’s involved and agree to have the treatment.

Read more about our consent process.

Before having Mohs surgery

Tell us if you’re allergic to any medicines, including local anaesthetics.

If you’re taking warfarin

Get a blood test to check your international normalised ratio (INR) levels 2 to 3 days before your surgery. You can do this at your local warfarin or anticoagulation clinic. If your INR is below 2 or above 3.5, contact us. We might need to reschedule your surgery.

Travel plans

Let us know if you have any plans to travel within 2 weeks after your surgery. If you do, we might reschedule your surgery so that you can recover safely.

On the day

You’ll usually need to come to hospital on more than 1 day to complete slow Mohs surgery.

Do not wear any makeup or jewellery near the area we need to remove.

The procedure can take several hours each day and you will not be able to leave the unit until it’s complete. Bring a packed lunch you can have while you wait.

It’s important you bring a friend or family member who can help you travel after you leave hospital. If possible, avoid using public transport immediately after your surgery.

Do not drive on the days of your surgery.

During slow Mohs surgery

Giving you local anaesthetic

Your doctor will inject the area around the tumour with a local anaesthetic. This makes the area numb so you do not feel any pain.

If you’re feeling very anxious about the surgery, we can also give you a mild sedative to help you relax. Talk to your doctor if you’d like to learn more about this.

For tumours near the eye, we might also use anaesthetic eye drops.

The local anaesthetic usually lasts for 2 hours. If it takes longer than this to remove the layer of skin, we can give you more local anaesthetic.

Removing the cancer

We’ll remove the visible part of the tumour, along with a small amount of healthy skin surrounding the tumour. We send this tissue to a lab, where we’ll examine it under a microscope to check for cancer cells.

It can take up to 3 days to get the results. We’ll put a dressing on your wound and give you instructions about when to come back to hospital.

If the results show that there are cancer cells in the surrounding tissue, we’ll invite you to another appointment to remove another layer of tissue.

We’ll repeat this process until the results show there are no more cancer cells.

After Mohs surgery

Repairing your surgical wound

Because we do not know how much skin we need to remove until we do the surgery, there are different options for how we repair your surgical wound.

The options include:

• coming back to our department so we can close the wound
• getting reconstructive surgery in the plastic surgery department
• leaving the wound to heal by itself under a dressing
• going to another hospital to repair the wound – in this case, we’ll give you a referral letter to give to your surgeon at the other hospital

Wound care

We’ll show you how to care for your wound so you can prevent infection and help it to heal. How you care for your wound depends on how big it is. Make sure you understand how to care for it before you leave hospital.

Going back to work

It’s important that you rest after having Mohs surgery. Take at least 2 days off work until you’re fully recovered.

Managing pain

If you need help managing pain, you can take aspirin-free painkillers, such as paracetamol or co-codamol.

Always check that the painkillers will not react with any other medicines you’re taking. Ask your doctor or a pharmacist for advice if you’re unsure.

Follow-up appointments

You’ll have a follow-up appointment with the team that repaired your wound.

If your follow-up appointment is at the Guy’s Cancer Centre, we’ll see you 1 week after your surgery. We’ll check that your skin is healing properly and remove any stitches.

If your wound was repaired by a different team, they’ll give you more information about a follow-up appointment.

More support

Living with cancer can be a difficult and emotional time. If you’d like support with this, or if you need someone to talk to, contact our Dimbleby Cancer Care service.

You can also refer yourself to the NHS talking therapies services.