Mohs micrographic surgery (MMS) for skin cancer

What is Mohs surgery?

A skin specialist (dermatologist) may use Mohs micrographic surgery (MMS) to remove your skin cancer. They remove one layer of the skin cancer at a time. During the operation they check each layer they remove under a microscope. They are looking for cancer cells.

They continue to remove layers until they can no longer see any cancer cells.

Mohs surgery aims to remove all the cancer cells, and leave behind as much healthy skin as possible.

When do you have Mohs surgery?

Mohs is a surgery treatment for some basal cell carcinomas (BCC). Doctors sometimes also use it to treat squamous cell carcinomas (SCC) and other rare skin cancers.

Your doctor will decide if you need to have Mohs surgery as not all skin cancers need it. They will discuss this with you.

You may have Mohs surgery for skin cancers that:

• have come back after treatment or when previous surgery has left some cancer cells behind

• are large and removing as little healthy skin as possible means a smaller scar

• are in areas where it's important to remove as little tissue as possible: for example, near the eyes, lips, ears or nose

• skin cancers which have unclear edges and there is a risk that other surgery types would leave cancer cells behind

Find out more about other types of surgeries for non melanoma skin cancer

What happens

As it is a specialised type of surgery, your doctor might refer you to another hospital to have treatment. Usually, a dermatologist who has specialised training in Mohs surgery does the surgery.

They examine your skin cancer and draw around the area with a pen.

You’re awake for your surgery. But you have an injection of medicine to numb the area (local anaesthetic).

The dermatologist removes the cancer and a small amount of healthy tissue (healthy margin). They put a dressing on the wound and ask you to wait.

They send the tissue to the laboratory and a specialist doctor (pathologist) looks at it under a microscope. They check if any cancer cells might be left. You can wait for up to 3 hours to get these results.

If the cancer is still there, then they’ll inject more local anaesthetic in the area and remove more tissue. You have to wait again.

Your dermatologist will continue to remove more tissue until they are sure all the cancer has gone and there is a surrounding area of healthy tissue.

How they close your wound depends on:

• where the cancer is

• how big your wound is

• your personal wishes

They might leave your wound to heal without stitches. You’ll have a dressing on top to protect it. Or they might use stitches to close the wound. In some cases, a plastic surgeon repairs your wound. This might be on the same day or very soon afterwards.

After surgery

You might be in the hospital all day for this surgery. You can go home after the surgery.

If you have non-dissolvable stitches, your practice nurse at the GP surgery can remove these after about one to two weeks.

When you go home your doctor or nurse will give you information about how to care for the wound. They will let you know when you need to go back for a check up.

Find out about follow up appointments

Side effects of surgery

Like all surgery, Mohs micrographic surgery has possible side effects. Some of these include:

• bleeding and bruising

• pain – you can take painkillers to help with this

• wound infection – your doctor might give you antibiotics to take

• nerve damage, such as numbness (this will usually improve in the weeks or months after surgery)

Contact the doctor who did the operation or see your GP if you are worried about your wound. 

Find out about other types of treatment for skin cancer