Mohs Surgery: Overview

In This Article

Mohs surgery, also called Mohs micrographic surgery, is a type of skin cancer surgery that removes skin cancer cells layer by layer. This meticulous technique helps surgeons preserve healthy skin while ensuring full removal of the cancer. In addition to having a very high cure rate, Mohs surgery is low-risk and can be completed in your doctor's office while you are awake and alert.

What Is Mohs Surgery?

Mohs surgery is done under local anesthesia by a highly experienced dermatologist who is fellowship-trained in performing this procedure. It's a scheduled procedure done in a surgical suite or doctor's office. Rarely, if the surgery is extensive, it may be performed in a hospital.

During Mohs surgery, thin layers of the skin cancer and surrounding tissue are removed by the dermatologist. The tissue is then taken to an on-site laboratory where it is evaluated under a microscope by a doctor called a pathologist.

While the tissue is being examined, the patient sits in a waiting area. If cancer cells are found, the patient goes back to the operating room for more tissue removal. This process is repeated until the removed tissue is cancer-free.

Alternative Surgical Technique

Depending on various factors, like the type, location, or size of a skin cancer, a standard surgical excision may be performed instead of Mohs surgery.

With a standard surgical excision, the abnormal skin growth along with a small amount of healthy tissue surrounding the growth (called the "margin") is removed. The margin is sent to the lab where it is examined under a microscope. If cancer cells are still present, the patient returns on another day to have more tissue removed.

Mohs surgery offers several potential benefits over a standard surgical excision.

These benefits include:

  • The procedure is completed in one day
  • A higher cure rate
  • More cost-effective
  • A better cosmetic result (smaller scar)

That said, two drawbacks to Mohs surgery is that the technique is usually more time-intensive (it can take several hours), and it can only be performed by a dermatologist who has specialized fellowship training.

Contraindications

There are no absolute contraindications to undergoing Mohs surgery.

Rather, the decision to perform this surgery depends on the expertise and experience of the surgeon, as well as criteria set forth by various professional societies, such as the American Academy of Dermatology and the American College of Mohs Surgery:

Purpose of Mohs Surgery

The purpose of Mohs surgery is to remove skin cancer while leaving as much healthy skin as possible.

Mohs surgery is most commonly used to treat high-risk basal cell cancer and squamous cell cancer.

Basal cell and squamous cell carcinomas are the most common types of skin cancer. They develop on the top layer of the skin (called the epidermis) and usually develop on skin-exposed areas, such as the face, head, and neck.

High-risk basal cell and squamous cell cancers include cancers that are:

  • Located on sensitive areas of the body like the face, neck, scalp, fingers, toes, or genitals
  • Large, growing rapidly or uncontrollably, or have poorly defined edges
  • Recurrent (meaning they have grown back)
  • Have an aggressive tissue pattern (determined by a skin biopsy before the surgery)

Besides basal cell and squamous cell cancers, Mohs surgery may also be used to treat other types of skin cancers, such as:

  • Lentigo malignant melanoma
  • Dermatofibrosarcoma protuberans (DFSP)
  • Extramammary Paget’s disease
  • Microcystic adnexal carcinoma
  • Merkel cell carcinoma
  • Sebaceous carcinoma

How to Prepare

Once your surgery has been scheduled, you will be given a set of instructions to help prepare you for your surgery.

These instructions may suggest the following: 

  • Take all of your medications as prescribed unless advised by your doctor
  • Stop certain medications (e.g., aspirin and ibuprofen) and herbal supplements (e.g., ginkgo biloba, vitamin E, or fish oil) for a period of time before surgery
  • Stop smoking, as this can increase your risk for acute postoperative complications, like infection or wound separation.
  • Stop alcohol for at least 48 hours before (and after) surgery to help prevent post-operative bleeding.

What to Expect on the Day of Surgery

On the actual day of your surgery, your surgeon will likely recommend the following:

  • Wear comfortable, loose-fitting clothes.
  • Eat a normal breakfast on the day of surgery.
  • Bring snacks and a book or an Ipad with you to occupy the time in between the tissue removal

Once you arrive at the outpatient center or clinic, your Mohs surgery will generally proceed with the following steps:

  • You will be positioned, either sitting up or lying down, on a surgical table.
  • A sterile drape will be placed over the area that is to be operated on.
  • The surgeon will inject a local anesthetic near the surgical site, which numbs the area completely.
  • The surgeon will remove the visible skin tumor, along with a portion of surrounding healthy tissue.
  • The surgeon will cut the tissue into sections and color code them with dyes. A diagram of the surgical site (called a Mohs map) is created.
  • The tumor and removed tissue will be taken to a special Mohs laboratory where a technician will freeze and cut the divided tissue into thin, horizontal slices. The slices of tissue will be stained, covered, and placed on microscope slides.
  • The slides will be examined under a microscope. If cancer cells are still present, more tissue will be excised.

Depending on the location and size of the tumor, your surgeon may allow the surgical site to heal on its own, or they may repair the site by using stitches. In some cases, reconstructive surgery is performed in which the wound is closed with a skin flap.

Post-Mohs reconstructive surgery is performed by a dermatologist or plastic surgeon and may be performed immediately after the skin cancer is removed or at a later date.

Recovery

After your surgery, you will have several follow-up appointments to ensure a healthy recovery. If stitches were placed, these are usually removed five to ten days after the surgery.

During your recovery, it's important to follow your surgeon's post-operative instructions. Following these instructions lowers your risk of infection and helps your skin wound heal more quickly.

These instructions may include the following:

  • Treat any pain with Tylenol (acetaminophen) as instructed.
  • Treat any swelling and bruising by applying an ice pack (not directly on the skin) every hour for twenty minutes for the first two days after surgery.
  • To minimize wound bleeding, avoid strenuous activities, exercise, bending, or heavy lifting for at least one week after surgery
  • Keep the would dry and covered for 24 hours
  • Bathe or shower the day after surgery and gently pat the wound dry

When to Seek Medical Attention

During your recovery, be sure to call your surgeon if you experience any of the following symptoms:

  • Severe, persistent, or worsening pain
  • Redness around the wound, especially if it is getting larger
  • Cloudy or white/yellow drainage from the wound site
  • Swollen lymph nodes near the surgical site

Long-Term Care

The benefit of Mohs surgery is that the cure rate is so high (more than 99%, for some tumors). Therefore, the chance of the cancer growing back (called a recurrence) is very unlikely. In addition, the amount of healthy tissue removed is minimized, which maximizes the aesthetic and functional outcome of the surgery.

In the long run, though, to prevent developing another skin cancer, your dermatologist will likely advise you on various sun-protecting strategies, such as:

  • Minimizing sun exposure as much as possible during peak hours of the day (10 am to 2 pm)
  • Wearing sunscreen, sunglasses, and a hat when going outside
  • Avoiding tanning (indoor and outdoor)

Your dermatologist may also advise you on performing self skin-checks in order to identify suspicious skin growths as early as possible.

Potential Risks

While uncommon, there are risks associated with Mohs surgery.

These risks include:

  • Wound opening or pulling apart (called dehiscence)
  • Necrosis (when the surgical wound tissue dies due to insufficient blood flow)
  • Bleeding and hematoma (when blood collects underneath the skin)
  • Infection
  • Damage to nerve endings in the skin resulting in numbness surrounding the wound site (this may last months or be permanent)
  • Scarring (which will occur with virtually any skin cancer treatment)

After Mohs surgery, the post-surgical scar may take up to one year to fully mature. During this time, the scar may appear red, or feel hard, bumpy, or itchy. These changes are usually temporary, but be sure to talk with your doctor if you have any concerns.

A Word From Verywell

Mohs surgery is truly a remarkable surgical technique. It leaves patients cancer-free while conserving as much skin as possible. That said, Mohs surgery should only be performed when indicated (sometimes, simple surgical excision is the best option) and by a physician who is highly-qualified and trained in this precise technique.

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