The Steps of Mohs Surgery

Mohs surgery is a special type of surgery that cuts out layers of the skin in stages until all the cancer is gone. It is done by a surgeon who has been specially trained to perform all the steps in the surgery. It is an outpatient procedure done in the Mohs surgeon’s office. That means you do not have to stay overnight at a hospital and can go home the same day. As with any treatment, there are risks you should talk about with your doctor and steps you will need to take to prepare for surgery. Learning all you can about how Mohs is performed, the risks, and the care needed can help you decide if it is the right treatment option for you.

How Mohs surgery is performed

Illustration of a surgery bed

Depending on where the cancer is, you will sit or lie down for the surgery, wearing either your clothes or a hospital gown.

Illustration of a special pen used for surgery

The surgeon looks at the cancer and uses a pen to mark up the area where the skin will be removed.

Illustration of a local anesthesia shot

You will be awake for the surgery but a medicine is used to numb the area being cut out so that you do not feel any pain.

Illustration of a cutting knife

When the skin is numb, the surgeon cuts out the skin cancer and a small area of normal looking skin around it. This may take about 10 to 20 minutes.

Illustration of a pressure dressing

After the skin is removed, a pressure dressing (bandage) will be put on the skin to help stop the bleeding. You may be told to sit in the waiting room while the skin that was removed is examined.

Illustration of a microscope

The skin is looked at under a microscope in the lab. This can take 40 to 50 minutes.

Illustration of a clock with a question mark instead of the hands of the clock

If skin cancer cells are found on the edge (margin) of the skin, you will go back to the room and have another stage of surgery. You will have as many stages as are needed until no more skin cancer cells are seen under the microscope; this is called “clearing the margins.” Most people will need 1 to 3 stages within the same day to remove all the cancer. Your surgeon will not know how deep the cancer is, how much skin will be removed, or how long the surgery takes until the surgery starts.

Illustration of a wound being closed

When the skin is cancer-free, the surgeon will talk about the options for closing the wound and reconstructive surgery, if needed. You are given care and follow-up instructions and can go home.

View the steps to learn how a specially trained surgeon performs Mohs surgery.

Why is Mohs surgery done in stages?

It may take the Mohs surgeon many stages of surgery before all the skin cancer is removed. The skin cancer you see on the outside of your skin is only some of the cancer. The rest is below the surface.

Illustration that shows the first step in a skin cancer surgery

Basal cell and squamous cell skin cancers appear on the outside of the skin. The cancerous cells are also found in deeper layers of the skin. The Mohs surgeon does not know how deep or wide the skin cancer is before the surgery.

Illustration that shows the second step in a skin cancer surgery

The surgeon will first remove a section of skin that has cancerous and healthy skin cells. That skin is looked at under a microscope. If cancerous cells are found on the outer part of the removed skin, the surgeon will take out more skin.

Illustration that shows the third step in a skin cancer surgery

The surgery is done again in as many stages as needed until all the skin cancer cells are removed.

Learn what to think about when deciding if Mohs is the right choice.

What to consider