Walk-in Dermatology > Blog > Medical Dermatology > What is Mohs Surgery and How does it Work?

What is Mohs Surgery and How does it Work?

March 1, 2021
Mohs Surgery | Dermatology

If you’ve just received a diagnosis of skin cancer, your physician may have recommended Mohs surgery as your best treatment option. That’s good news, because Mohs surgery is one of the most effective cancer treatments available.

Mohs Surgery Procedure

Mohs surgery is a microscopically controlled procedure dermatologists use for treating common types of skin cancer. The surgeon gradually removes skin tissue in layers, pausing after each layer to examine the tissue for cancer cells while the patient waits. The entire procedure is almost always done in a single visit.

For historical context on how long this procedure has been used, Mohs was developed in 1938 by Dr. Frederic E. Mohs at the University of Wisconsin. While Mohs is nothing new, you’ll want to make sure that if you’re having this procedure performed, it’s done so only by a dermatologist with specialized surgical training in Mohs procedures.

Mohs surgery is considered the most effective technique for treating many basal cell carcinomas and squamous cell carcinomas, which are the two most common types of skin cancer. Sometimes called Mohs micrographic surgery, the procedure is done in stages, usually in just one visit. The goal is to remove all cancerous cells while saving healthy tissue and leaving the smallest possible scar. The practice of Mohs surgery became widespread in the 1960s as surgeons realized the benefits of the procedure for dermatology.

There are three main steps in Mohs surgery:

  • Removal of cancerous skin tissue layer by layer
  • Analysis of the skin tissue
  • Closure or reconstruction of the skin surrounding the surgery area

Mohs surgery has a high success rate. It is also an efficient and cost-effective treatment that typically involves only outpatient surgery. The entire procedure, including lab work, is performed on-site while the patient waits under a local anesthesia. Mohs surgery also offers the highest cure rate for basal and squamous cell carcinomas. Statistics show a 99% cure rate for a skin cancer that has not been treated before and up to a 94% cure rate for a skin cancer that has recurred after a previous treatment.

Here’s how Mohs Works:

Once the patient is comfortable and receives a local anesthetic to numb the area for treatment, the Mohs surgeon begins by removing a layer of skin tissue. That sample is then given to a histotechnician who processes the tissue and places it on slides in the dermatologist’s on-site lab. The Mohs surgeon then examines the tissue under a microscope. If any cancer cells still remain, the surgeon knows the precise area for removing another layer of tissue. The goal is to save as much healthy tissue as possible to reduce scarring. The surgeon repeats the process until all cancer cells are removed.

Examination and prep

Your Mohs surgeon examines the spot where you had your biopsy. Depending on the location of the skin cancer, you may be able to wear your clothes or you might need to put on a hospital gown. You might need to lay down or remain seated as well. This also depends on the area being treated. Your surgeon will give you an injection of a local anesthetic, which numbs the area. You’ll remain awake throughout the procedure, but you won’t feel a thing.

First layer removal

Your surgeon will use a scalpel to slice a thin top layer of cancerous tissue. This layer is then examined microscopically to determine if the cancer extends deeper into the skin. After this lab analysis, your surgeon may need to remove another thin layer from the same location and check it under the microscope.

Lab work

Each tissue layer is further sliced into sections and color-coded with dyes. The tissue is then frozen and cut in thin horizontal slices. These are mounted on microscope slides by the histotechnician.

Microscopic analysis

Your Mohs surgeon will examine all edges and the underside of the tissue to determine if any cancer cells remain. If so, the surgeon will remove another tissue layer.

Additional layer removal

Your Mohs surgeon will administer more anesthesia if necessary before removing the next tissue layer. The lab work and examination under a microscope is repeated.

Completing the surgery

When there is no more evidence of cancerous skin cells, your Mohs surgeon will either dress the area with bandages or, if necessary, suture it with stitches. Larger areas may require a skin graft and in cases where extensive Mohs surgery is necessary, a plastic surgeon may be needed to reconstruct the affected area.


Your surgeon will provide full post-operative instructions for wound care, scar treatment and follow-up. That’s it. Mohs surgery is a safe, highly effective and cost-efficient treatment for the two most common forms of skin cancer.

The Mohs Surgery Process - ACMS

Let Walk-in Dermatology Take Care of You and Your Skin

If you suspect you might have skin cancer, or if you’ve missed your annual full body skin exam, there’s no need to wait, worry or wonder. Walk-in Dermatology is here to keep you healthy. Our team of board-certified dermatologists and experienced medical staff will address your concerns and provide the necessary care for all your skin conditions. You can also schedule an appointment with us online.

If you can’t make it to one of our offices, we can set up a Video Visit and even prescribe medications remotely. Contact us today.