Mohs surgery is used to treat skin cancer. This includes common types of skin cancer, such as basal cell carcinoma and squamous cell carcinoma. It also includes melanoma and other less-common skin cancers.

Mohs surgery is most useful for skin cancers that:

• Have a high risk of coming back or that have returned after previous treatment.
• Are in areas where you want to keep as much healthy tissue as possible. This includes areas around the eyes, ears, nose, mouth, hands, feet and genitals.
• Have edges that are hard to define.
• Are large or grow quickly.

Problems that can happen during and after Mohs surgery include:

• Bleeding
• Pain or tenderness around the places where surgery was done
• Infection

Other problems that can happen are less common. They may include:

• Temporary or permanent numbness of the surgical area. This can happen if small nerve endings are cut.
• Temporary or permanent weakness of the surgical area. This can happen if a muscle nerve is cut to remove a large skin cancer.
• Shooting pain in the area.
• A large scar.

Your surgeon may recommend ways you can prepare for your surgery. You may be asked to:

• Stop taking certain medicines. Tell the surgeon what medicines or supplements you take. Be sure to mention any medicines that thin the blood. Some supplements may make you bleed more after surgery. That's why you want to make sure your surgeon knows about the supplements you take, too. Continue taking any prescription medicines unless your surgeon tells you to stop.
• Clear your schedule for the day. It's not possible to know how long your Mohs surgery will take. For most people, the procedure takes less than four hours. Your surgeon may tell you to plan for the surgery to take all day, just in case it might. But there's a very small chance it could take that long.
• Wear comfortable clothing. Wear casual clothes that are comfortable. Dress in layers in case the room is warm or cold.
• Bring something to help pass the time. Expect some waiting time during your Mohs surgery. Bring a book, magazine or other activity to help you pass the time.
• Eat before surgery. It's usually OK to eat before your appointment. Unless a member of your health care team tells you differently, you can eat your usual meals.

You typically go to an outpatient surgery center or doctor's office for Mohs surgery. The procedure is done in an operating room or procedure room. The room has a lab nearby.

Most of the time, the procedure takes less than four hours. But it can be hard to tell how large a skin cancer is just by looking at it. So health care providers often recommend planning for the procedure to take the whole day.

You probably won't have to wear a surgical gown unless the location of the cancer requires it. The area of skin to be operated on is cleaned and then outlined with a special pen. After that, you are given a shot in the area with medicine called a local anesthetic. The shot might hurt for a few seconds, and then the medicine numbs the skin. This is done so you won't feel any pain during the procedure.

During the procedure

After the anesthetic takes effect, the surgeon uses a knife called a scalpel to remove the visible portion of the cancer. The surgeon also takes a thin layer of tissue underneath and around the cancer. A temporary bandage is placed where the skin was removed. This takes only a few minutes.

The tissue is then taken to the lab for analysis. This part of the procedure usually takes the longest time.

You'll wait about an hour in a waiting room. It may help to bring a book or magazine to pass the time. You can use the restroom or have a snack if you need to. But you won't be able to leave until the procedure is done.

The surgeon or a technician cuts the tissue sample into sections and looks at them with a microscope. The surgeon makes a map to keep track of the exact spot where each piece of tissue was removed. So if a small area of cancer is found in one piece of tissue, the surgeon knows where to continue with the operation.

If there is more cancer, your Mohs surgery continues. The surgeon removes an additional layer of tissue from the affected area. The surgeon takes care to remove tissue that contains cancer and leave as much healthy tissue as possible. Again, you'll wait while the surgeon looks at the tissue in the lab.

This process continues until the last tissue sample removed is cancer-free. You may get another shot of local anesthetic if necessary.

After the procedure

After all of the cancer has been removed, you and your surgeon can decide on how to fix the wound. This could include:

• Letting the wound heal on its own
• Using stitches to close the wound
• Pulling skin from a nearby area to cover the wound
• Using a piece of skin from another part of the body, such as behind the ear, to cover the wound

Most wounds are repaired at the end of the Mohs surgery. If the wound is large or complex, the surgeon may temporarily close the wound. Another operation might be needed to repair the wound, though this is rare.

You may have some mild pain and soreness after your surgery. Pain medicines you can buy without a prescription may help. Severe pain after surgery is not common. Contact your health care provider if your pain is severe.

Expect to wear a bandage over the wound for a week or longer. Though exactly how long you'll need a bandage depends on your situation. Your provider will give you instructions on how to take care of the wound. You may be asked to change the bandage every day.

One of the advantages of Mohs surgery is that you know your results right away. You usually don't leave your appointment until all of the skin cancer has been removed. You may have another visit with your surgeon or primary care provider to make sure your wound is healing correctly.