Mohs Surgery for Skin Cancer

Skin Care
Mohs Surgery (Source: Clinical Dermatology, Habif)

In the world of skin cancer management, a procedure called “Mohs Surgery” comes up often. The surgery was invented in the 1930s by Dr. Fredric Mohs. Sometimes, it is mistakenly thought to be “Moh’s surgery.”

Who does Mohs Surgery?

Even though Dr. Mohs was a general surgeon, the technique was widely accepted and used at first by dermatologists. Surgeons were resistant to the part where they would have to study the removed tissue histologically the way dermatologists do. But now it is performed more and more by surgeons as well.

Who needs Mohs Surgery?

It is employed in curing different forms of skin tumors, especially basal and squamous cell carcinoma. Mucus membrane cancers, such as inside the mouth and nose, are also treatable using Mohs surgery.

As for melanoma, Dr. Mohs tried promoting the use of his procedure for melanoma for a long time, but it was rarely used at first for fear of spreading the melanoma further. However, recent advances have encouraged more and more dermatologists to start using Mohs for melanoma as well.

What is Mohs Surgery?

Sequence of events

The problem with removing a skin tumor is not knowing where the tumor ends and normal skin begins. In order to avoid leaving any diseased skin, the solution was to remove so much “safety margin” that you risk removing too much normal skin, which leaves the shape of the treated area less than desirable for the patient.

Mohs surgery eliminates the guesswork. Basically the tumor is removed one thin layer at a time. Each layer is examined under histologically to ascertain it still contains abnormal skin. When a layer is reached where all skin is normal, the procedure ends there. As a result, much less tissue is removed. The area treated can then be reconstructed. All of this is done in one setting.

This is particularly useful in areas where you can’t afford to lose too much skin, such as the eyelids, the nose, the ears, and the fingers. This is because reconstruction is more difficult when too much tissue is lost. It is also useful in areas where cosmetic appearance is important. You don’t want to leave a large scar on the face on in areas of the body that you like to leave exposed, such as the arms. Reconstruction is difficult in areas such as the tip of the nose or the lips.

The surgery underwent several advances over the years. Today, rather than requiring multiple settings to perform the entire procedure, the surgery can be done in a single day.

Pros of Mohs Surgery

  • Mohs surgery has a high cure rate.
  • It is an outpatient procedure, is usually done in one day.
  • There is no general general anesthesia.
  • Only cancerous tissue is removed, retaining plenty of healthy tissue for a proper reconstruction of the treated area.

Why isn’t Mohs Surgery used to treat ALL skin cancers?

H zone: areas on the face where Mohs should be considered (Source: first in sources)

There are two major reasons why Mohs is not used with every single skin cancer situation: The procedure is very long and tedious (for both surgeon and patient), and the process requires a dermatologist/surgeon with excellent experience in pathology and very steady hands. This particular skill is not as common as desired, and an unskilled pathologist can obtain quite incorrect results, rendering this technique essentially ineffective.

In general: if a basal cell carcinoma is primary (first time occurring), smaller than 2cm, slow growing with well defined borders and a non-aggressive histology type, then methods such as radiation, excision or cryosurgery can be used to remove it.

If the basal cell carcinoma is a recurrent one, larger than 2 cm, fast growing with ill defind borders and an aggressive histology type, then Mohs surgery is a better option.

Criteria for squamous cell carcinoma differ slightly as smaller diameters are treated with Mohs.

Only tumors that are aggressive or recurrent or are in areas that are hard to reconstruct, are treated using Mohs surgery.

Thank you for reading!


NA. Swanson et al. Mohs Surgery: Techniques, Indications and Applications in Head and Neck Surgery. Head and Neck Surgery 2006; 6 (2): 683-92.

RP. Rapini. Pitfalls of Mohs Microscopic Surgery. Journal of the American Academy of Dermatology 1990; 22 (4): 681-6.

TP. Habif. Clinical Dermatology. Fifth Edition. Mosby 2009; Chapter 27.

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  • Having had this procedure myself a few years ago, I want to add two things. First, I’m glad I didn’t have to lose more of my forehead. Second, it’s not exactly a picnic. While I’m glad basal cell has such a high cure rate, having anything cut out of your skin is unpleasant at best. Wear sunscreen/ block. Stay out of the sun. For real. You’ll still be in some pain and under restrictions on your normal activities until the stitches are out.

    • @Emily
      Those are a couple of excellent points. Certainly going through this procedure is not easy. I am glad you are doing better now. Thank you so much for adding this advice and for sharing your experience.

  • This is so cool! The nerdy side of me loves reading about medical procedures (:

    • @Tiffany Martin
      Glad you liked it! And thank you so much for saying so, makes me happy 🙂

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