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Mohs micrographic surgery (MMS)

Mohs micrographic surgery is also called margin controlled excision. It is a specialist type of surgery that aims to remove all the skin cancer and leave as much healthy skin tissue as possible.

As it is a specialised type of surgery, your doctor might refer you to another hospital to have the treatment.

When do you have it

Mohs micrographic surgery (MMS) is most useful for:

  • basal cell cancers that have come back after removal or have not been completely removed
  • basal cell cancers that have grown in an area that has had surgery or radiotherapy before
  • basal cell cancers that are growing into surrounding skin tissue
  • large skin cancers where removing as little of the healthy skin tissue as possible can mean a smaller scar
  • cancers in areas where it's important to remove as little tissue as possible: for example, near the eyes, lips, ears or nose
  • some rare skin cancers

How you have it

Your doctor draws around the skin cancer with a pen.

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

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

The doctor sends the tissue to the laboratory and a specialist doctor (pathologist) looks at it under a microscope. They look to see if any cancer might be left. You can wait for up to an hour to get these results.

If the cancer is still there, the doctor injects more local anaesthetic in the area and removes more tissue. You then wait again.

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

Your doctor 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, another surgeon (such as a plastic surgeon) repairs your wound. This might be on the same day or very soon afterwards.

After surgery

You can go home after surgery.

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

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.

Side effects of surgery

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

  • bleeding and bruising
  • wound infection – your doctor might give you antibiotics to take
  • nerve damage, such as numbness (this will 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. 

Last reviewed: 
07 Oct 2019
  • MOHS MICROGRAPHIC SURGERY
    British Association of Dermatologist
    Patient Information Leaflet 2016

  • Service Guidance and Standards For Mohs Micrographic Surgery
    British Association of dermatologists, March 2019

  • Rook’s Textbook of Dermatology (9th Edition)
    C Griffiths and others
    Blackwell Publishing Ltd, 2016

  • Pfenninger & Fowler’s Procedures for Primary Care (3rd Edition)
    J L Pfenninger and G C Fowler
    Elsevier Mosby, 2011

  • Improving outcomes for people with skin tumours including melanoma (update)
    National Institute for Health and Care Excellence (NICE), 2010

  • Non-melanoma skin cancer: United Kingdom National Multidisciplinary Guidelines
    C Newlands and others
    The Journal of Laryngology and Otology, 2016. Volume 130, Supplement 2, Pages S125 – S132