What Is Mohs Surgery?

Medically Reviewed by Stephanie S. Gardner, MD on February 21, 2024
4 min read

Doctors use Mohs surgery (also called Mohs micrographic surgery) to treat skin cancer. The goal is to remove as much of it as possible while saving the healthy tissue around it. Layers of skin are removed one at a time and examined under a microscope until all the cancer is gone. This reduces the chance of needing future treatments or surgery.

A doctor named Frederick Mohs developed the treatment in the 1930s. While newer ones have come along in recent years, many surgeons still rely on this procedure to treat skin cancer. It is considered the most effective treatment for two of the most common types of skin cancer: basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). It can also be used to treat other kinds of skin cancers.

Mohs surgery is best in these situations:

  • Your skin cancer is likely to come back or has already returned since your last treatment.
  • It’s located in a part of your body where it’s important to keep as much healthy tissue as possible.
  • It’s especially big or grows fast.
  • It has uneven edges.

Mohs surgery is done in an operating room or office with a nearby lab. That way the surgeon can easily examine the tissue once it’s removed. The surgery usually lasts about 4 hours, and you’ll go home the same day. But it can last longer, so set aside the whole day for it.

Before your surgery, a doctor or nurse will clean the area. They’ll then use a special pen to outline it and inject your skin with medicine so you won’t feel any pain.

The surgeon will remove the visible part of your cancer with a scalpel. They’ll also remove a thin layer of tissue under the visible tumor and put on a temporary bandage. The tissue will then be taken to the lab to be looked at under a microscope. If there’s still cancer, more layers will be removed, one at a time, until no more cancer can be seen.

Cutting away the skin might take just a few minutes, but the analysis can take much longer, maybe up to an hour. You may want to bring a snack to eat or something to read to help pass the time.

Once your surgeon has removed all of the tissue that contains cancer, they’ll discuss your options for how to let the wound heal. Depending on your situation, they’ll go with one of these:

  • Stitch the wound closed.
  • Let the incision heal by itself.
  • Take a flap of skin from a nearby part of your body to help cover the wound.
  • Take a skin graft from another part of your body to help cover the wound.
  • Temporarily close the wound and set reconstructive surgery for later.

Because your surgeon will be able to see the results right after the tissue is removed, you’ll likely go home with all your skin cancer removed. But you may need to follow up with your doctor just to make sure your recovery is going well.

You may have discomfort, bleeding, redness, or swelling after the procedure, but these issues should go away on their own before long. Your doctor will give you instructions on how to clean the wound and about any medicine you need to take.

It’s a good idea to have someone take you home afterwards. If you’re taking sedatives or prescription painkillers, driving yourself home is not an option.

Mohs surgery has the highest cure rate of all treatments for basal cell and squamous cell carcinomas -- more than 99% for new skin cancers and 95% if the cancer comes back.

Your doctor will want to schedule regular follow-ups with you to check your skin for new cancers. Twice a year is normal, but you may need them more often if the cancer is an aggressive type that’s more likely to come back. You and your doctor will decide on the right schedule.

Mohs surgery is generally considered very safe, but there are some risks:

  • Bleeding from the site of surgery
  • Bleeding into the wound (hematoma) from surrounding tissue
  • Pain or tenderness in the area where skin was removed
  • Infection

Although these are less likely to happen, there are other potential problems:

  • You could have temporary or permanent numbness in the area where the skin was removed.
  • If your tumor was large and your surgeon cut a muscle nerve while removing it, you might feel some weakness in that part of your body.
  • You might feel itching or shooting pain.
  • You could develop a thick, raised scar.