Mohs Surgery

Overview

What is Mohs surgery?

Mohs surgery (also known as Mohs micrographic surgery) is a method used to remove high-risk skin cancer. It’s very precise. Your surgeon cuts away (excises) the tumor in layers starting with the visible portion of the tumor and a margin of skin cells around it. Then, the sides and deep edges are examined under a microscope. If the skin cancer extends to any of the edges (margins) your surgeon will remove more tissue in the positive areas, and look at the new sample under a microscope. This process continues until all of the cancer is removed.

One of the advantages of Mohs surgery is that your surgeon only removes cancerous tissue. This means that your healthy tissue is spared, making Mohs a useful approach for skin cancers on your face, scalp, ear, hands, feet and genital areas.

Why is it called Mohs surgery?

The procedure was developed by Frederic E Mohs, MD, in the 1930s and has since been refined. Originally, Dr. Mohs injected the tumor with a preserving chemical so that when removed (excised), he could inspect the tissue under a microscope. But the initial process of preparing fixed-tissue slides took several days, the use of chemicals to cauterize the tumor was controversial and the procedure was painful.

About 20 years passed before Dr. Mohs and his colleagues tried a new technique to remove carcinoma from an eyelid: the surgery could be done in one day using frozen fresh tissue in slide preparation.

Mohs surgery vs. excision: What’s the difference?

Excision is a procedure through which your surgeon removes the skin cancer and a margin of surrounding skin and the specimen is sent to pathology for processing and interpretation. In general, less than 1% of the margins are checked with wide local excision. . Mohs micrographic surgery involves excision with a smaller margin and the tissue is processed in such a way that your surgeon checks 100% of the deep and side (lateral) margins.

What types of skin cancers are removed with Mohs surgery?

The Mohs surgery procedure treats the most common forms of skin cancer: basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). Mohs surgery is also sometimes used to treat other skin cancers, including certain melanomas, dermatofibrosarcoma protuberans, microcystic adnexal carcinoma, sebaceous carcinoma and extramammary Paget disease, among others.

Where is Mohs surgery done?

Mohs surgery is done in a doctor’s office or outpatient surgical center. After each excision, you’ll wait in a waiting room or the operating room while your care team prepares slides of your tumor and your surgeon inspects those slides. If your provider finds tumor at any of the margins, you will be brought back in so your surgeon can remove another layer of tissue for further inspection. This process can take a while, so be sure to bring a book or electronic device to keep you occupied while you wait.

How often are these procedures performed?

Mohs surgery is a very common treatment for high-risk skin cancer because it has a cure rate of up to 99%. This is the lowest recurrence rate of any other treatment for skin cancer.

Procedure Details

What happens before Mohs surgery?

Before you have a Mohs surgery for skin cancer, you’ll see your dermatologist for a physical exam of the site and surrounding tissue. Together, you and your dermatologist will review:

  • Your medical history and any medications or supplements you take.
  • The results from your biopsy.
  • Your diagnosis of skin cancer, including your treatment options and the risks and benefits of Mohs surgery.

Depending on your general health and the location of the surgical site, you may need to take preoperative antibiotics.

How is Mohs surgery performed?

The Mohs procedure involves a layer-by-layer removal of skin that contains cancer cells. Here are the typical steps in the procedure:

  • Your surgeon numbs the skin around the cancer cells with an injected anesthetic.
  • They remove any visible, raised area of the tumor.
  • They also remove a thin layer of tissue from the site. Your surgeon will try to preserve as much healthy, normal skin as possible.
  • They mark the tissue so they can identify the right, left, top and bottom, and create a map of the site.
  • They immediately freeze, cut and stain the tissue the doctor's office. This process takes approximately one hour, but this time varies from case to case.
  • Your surgeon examines the entire bottom and outer edges of the removed tissue layer under a microscope.
  • If there are any cancer cells in the sample, your surgeon identifies their precise location (according to the markings and map), and removes an additional thin layer of tissue from the area where cancer cells remain.
  • The process of microscopic examination and removal of additional layers of tissue continues until there are no more cancer cells. Will I need reconstruction of the resulting wound?

Will I need reconstruction of the resulting wound?

After complete removal of the skin cancer, your surgeon will discuss the best method of managing your wound. The choices include:

  • Letting your wound heal on its own (second intention healing).
  • Closing your wound with stitches (sutures).
  • Closing your wound with a skin flap (borrowing tissue from surrounding skin) or a graft (borrowing tissue from another site on your body).
  • A combination of the approaches listed above.
  • Involving another surgical specialist like an oculoplastic (around the eye) or facial plastic surgeon (usually reserved for a larger than expected tumor).

Are you awake for Mohs surgery?

Yes, most people are awake for Mohs surgery. Your surgeon will numb the area with injected medications (anesthetics). You will feel pressure and touch but no pain, and you’ll rest comfortably in the waiting room or in the operating room while they analyze your tissue. If you need more skin removed, you may still be numb from the initial injections, or more injections may be needed.

What if I’m anxious about surgery?

It’s quite common to feel anxious before a procedure. Your healthcare provider may recommend a variety of techniques to calm your nerves. During the procedure, you may want to listen to music or a guided meditation. Your provider may also give you antianxiety medication before the procedure.

How long does Mohs surgery take?

Mohs surgery may take only a few hours, or it may take the whole day. How long the procedure takes depends on the tumor itself: bigger, deeper tumors take longer to remove completely.

Risks / Benefits

How successful is Mohs surgery?

Mohs micrographic surgery has the highest cure rate of all treatments for basal cell and squamous cell skin cancers. For basal cell carcinoma, the cure rate is up to 99% for new cases and up to 94% for recurrent cases. For squamous cell carcinoma, the cure rate is 95% to 99% for new cases and 90% for recurrent cases.

What are the advantages of having Mohs surgery?

The most important advantages of Mohs surgery are the complete microscopic examination, which allows for complete removal of the cancer and high cure rates, and the ability to spare as much normal skin as possible.

Additional advantages of Mohs surgery for skin cancer include:

  • It’s done in a single outpatient visit.
  • You’ll receive local anesthesia to numb the area, so you’ll recover faster compared to general anesthesia or sedation.

Are there risks associated with Mohs surgery?

The risks associated with the Mohs surgery itself are very low. Please discuss your particular health issues and any concerns about the Mohs procedure with your surgeon. Listed below are the usual risks associated with Mohs surgery:

  • Scar formation.
  • A larger than expected wound.
  • Poor wound healing.
  • Excessive bleeding.
  • Infection.
  • Loss of nerve function (muscle or feeling), which can be temporary or permanent.
  • Regrowth of tumor after removal (more common with previously treated tumors and large, longstanding tumors).

Recovery and Outlook

How much pain is there after Mohs surgery?

Most patients report mild to moderate pain following Mohs surgery. The pain goes away gradually over a few days and can be effectively managed with acetaminophen (Tylenol®). Individuals who have Mohs surgery on their scalp or whose wound is larger than 3 square centimeters tend to report more pain than those who have the procedure on other areas.

How long does it take to heal from Mohs surgery?

Scars from Mohs surgery continue to heal for 12 to 18 months after your procedure. In the year following Mohs surgery, you’ll want to be patient as your scar matures, then fades. If you’re unhappy with your scar, talk to your surgeon about your options for scar revision.

How can I take care of myself while I’m healing from Mohs surgery?

Following Mohs surgery, you’ll want to take care of yourself to allow for optimal healing. Your surgeon will give you instructions for aftercare following Mohs surgery. When you go home, you’ll have a dressing on your wound. Leave it undisturbed for the first 24 to 48 hours, or as directed by your surgeon. After that initial period of healing, remove the dressing for wound care two times a day or as directed. To care for your wound, cleanse with 3% hydrogen peroxide or a mild soap, then cover your wound with petroleum jelly and cover it with a dressing that won’t stick to your wound. Once the dressing is no longer needed, be sure to protect your scar using sunscreen with a sun protection factor (SPF) of at least 30, as well as protective hats during any sun exposure.

Your surgeon will also instruct you to:

  • Avoid strenuous exercise and heavy lifting for at least a week.
  • Apply ice or cold packs regularly in the days following surgery to reduce swelling and bruising – just be sure not to put the ice directly on your skin.

How long should I use Vaseline® after Mohs surgery?

You should cover your wound with petroleum jelly (Vaseline®) at least until your sutures are removed (one to two weeks). At this follow-up visit, your surgeon will take a look at the area to see how your wound is healing. They may instruct you to use petroleum jelly for another couple of weeks.

When to Call the Doctor

When should I call my doctor after Mohs surgery?

Following any surgery, you should feel comfortable calling your doctor with questions about the procedure or how you’re healing. You should also call your surgeon if you experience:

Bleeding

It’s normal to have a little bleeding or oozing from the wound, especially in the first few hours after surgery. Applying pressure to the wound should stop the bleeding, but call your surgeon if the bleeding doesn’t stop.

Pain

You can expect to have some mild to moderate pain or discomfort following Mohs surgery. Call your surgeon if:

  • You can’t manage the pain with acetaminophen (Tylenol®).
  • The pain doesn’t go away after a few days.
  • The pain starts to get better and then gets worse.

Signs of infection

An infected wound can lengthen your recovery time and make your scar heal less optimally. . You may need topical or oral antibiotics. Contact your surgeon if:

  • You develop a fever.
  • You notice a thick, yellowish discharge or foul smell odor
  • The area around your wound is bright red.
  • The skin around your wound is swollen and hot to the touch.

A note from Cleveland Clinic

Hearing the word “cancer” from you doctor can be scary. But if your skin cancer is caught early — before it spreads to other areas — it’s possible that you’ll be cured in a single day with a precise procedure called Mohs micrographic surgery. In Mohs surgery, your surgeon removes your tumor, layer by layer. Each layer is carefully labeled and examined under a microscope to look for cancer. If cancer cells remain, your surgeon removes and examines another layer until the cancer is completed gone.

Last reviewed by a Cleveland Clinic medical professional on 08/31/2022.

References

  • American College of Mohs Surgery. About Mohs Surgery. (http://www.skincancermohssurgery.org/mohs-surgery/) Accessed 8/31/2022.
  • Brodland DG, Amonette R, Hanke CW, Robins P. The history and evolution of Mohs micrographic surgery. (https://pubmed.ncbi.nlm.nih.gov/10759814/) Dermatol Sur. 2000 Apr;26(4):303-307. Accessed 8/31/2022.
  • Greenway HT, Maggio KL, Lane BS, Cao T, Khachemoune A. Mohs Micrographic Surgery and Cutaneous Oncology. In Robinson JK, Hanke CW, Sigel DM, Fratila A, eds. Surgery of the Skin, 3rd ed. New York, NY: Elsevier, 2015, pp 702-728.
  • Limthongkul B, Samie F, Humphres TR. Assessment of postoperative pain after Mohs micrographic surgery. (https://pubmed.ncbi.nlm.nih.gov/23464845/) Dermatol Surg. 2013 Jun;39(6):857-863. Accessed 8/31/2022.
  • Prickett KA, Ramsey ML. Mohs Micrographic Surgery. (https://www.ncbi.nlm.nih.gov/books/NBK441833/) In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Accessed 8/31/2022.
  • Skin Cancer Foundation. Mohs Surgery. (http://www.skincancer.org/skin-cancer-information/mohs-surgery) Accessed 8/31/2022.

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