Mohs Surgery: The Gold Standard for Removing Skin Cancer

What Is Mohs Micrographic Surgery?

Mohs micrographic surgery (often just called “Mohs surgery”) is a specialized, tissue-sparing surgical technique for removing skin cancer. It was developed in the 1930s by Dr. Frederic Mohs and refined over the following decades into the precise procedure used today.

What makes Mohs unique is that the surgeon acts as both the operating physician and the pathologist. After each thin layer of tissue is removed, the surgeon personally maps, processes, and examines the entire undersurface and edges of the specimen under a microscope—right there in the office—before deciding whether more tissue needs to be removed. This “stage-by-stage” approach means:

• Up to 100% of the surgical margins are examined (vs. about 1–2% in standard excision)
• Only tissue that actually contains cancer is removed—healthy tissue is preserved
• Cure is confirmed the same day before the wound is repaired

Who Is Mohs Surgery For?

Mohs surgery is recommended for specific situations where its precision matters most. According to guidelines from the American Academy of Dermatology, Mohs is appropriate for:

• Skin cancers in high-risk areas: Face (especially nose, ears, eyelids, lips), hands, feet, genitals, and scalp—where preserving normal tissue is especially important
• Recurrent skin cancers: Cancer that has come back after a previous treatment
• Aggressive cancer subtypes: Morpheaform or infiltrative basal cell carcinoma; poorly differentiated squamous cell carcinoma
• Cancers with ill-defined borders: Where the edges of the tumor are hard to see clinically
• Large tumors: Especially those over 2 cm in diameter
• Patients who are immunocompromised: Including transplant recipients, who are at higher risk of recurrence

Mohs is most commonly used for basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), which together account for about 5.4 million cases in the US each year.

How Is It Different from Standard Excision?

In standard excision, the surgeon removes the visible tumor plus a margin of normal-looking tissue and sends the whole specimen to a pathology lab. Results come back in 3–5 days. The lab usually examines only a small percentage of the margins (called “bread-loaf” sectioning). If margins are involved, the patient must return for a second surgery.

In Mohs surgery, the surgeon examines the entire margin—all the way around and under the tumor—in real time. If cancer cells are seen under the microscope, only that specific area is re-excised. This process repeats, one precise layer at a time, until no cancer remains. The average Mohs case requires 1.5–2 stages to achieve clear margins.

What to Expect on the Day of Surgery

Mohs surgery is done as an outpatient procedure, but plan for it to take a full day. You will not know in advance exactly how long it will take because it depends on how many stages are needed.

1. Arrival and preparation: The surgical area is cleaned and marked. Local anesthesia is injected. The numbing process takes 5–10 minutes to work fully.
2. First stage: The surgeon removes a thin layer of tissue just below and around the visible tumor, oriented precisely and color-coded for mapping. A temporary dressing is applied to the wound.
3. Waiting period: You wait—usually 45 minutes to an hour—in the waiting room while the tissue is processed and examined under the microscope. Bring a book, headphones, or something to keep you occupied. The waiting room is often shared with other patients at different stages of their procedure.
4. Results and next step: The surgeon reviews the map and either:
   • Tells you the margins are clear and proceeds to wound closure, or
   • Numbs a specific area and removes another targeted layer of tissue (another stage)
5. Wound repair: Once all margins are clear, the wound is repaired. Depending on its size and location, this may be direct closure (stitching the wound shut), a skin flap (rearranging nearby tissue), a skin graft, or in some cases allowing the wound to heal naturally (secondary intention). The repair can take additional time.

Recovery After Mohs Surgery

Recovery depends largely on the size of the wound and how it was repaired:

• Small wounds closed directly: Mild soreness for a few days; stitches out in 5–14 days depending on location; return to normal activities within a week
• Flap or graft repairs: May require more activity restriction, pressure dressings, and multiple follow-up visits over several weeks
• Secondary intention healing: The wound is left open and heals slowly on its own over several weeks; requires daily wound care

General post-operative instructions include: keep the wound clean and moist with petroleum jelly, change dressings daily, avoid strenuous exercise for 1–2 weeks, and protect the scar from sunlight for at least 6 months.

When to See a Dermatologist

• You have been diagnosed with basal cell carcinoma or squamous cell carcinoma and want to understand all your treatment options
• Your skin cancer is on your face, ears, nose, eyelids, or another cosmetically or functionally important area
• You have had a skin cancer that has come back after previous treatment
• Your pathology shows an aggressive cancer subtype
• You have a weakened immune system and are diagnosed with skin cancer

Frequently Asked Questions

Is Mohs surgery always the best option?

Mohs is the best option for specific situations described above, but not every skin cancer needs it. Many small, low-risk BCCs in non-critical locations can be treated effectively with standard excision, electrodesiccation and curettage, or even non-surgical options like topical creams or photodynamic therapy. Your dermatologist will help you choose the right treatment based on the type, location, size, and behavior of your cancer.

Will I be put to sleep?

No. Mohs surgery is performed entirely under local anesthesia. You are awake the entire time. This is actually an advantage—it makes the procedure safer than general anesthesia and allows you to drive home afterward in most cases.

What are the cure rates for Mohs surgery?

For primary (first-time) basal cell carcinomas, Mohs surgery has a 5-year cure rate of approximately 99%. For recurrent BCCs (those that came back after prior treatment), the cure rate is about 94–96%. For primary squamous cell carcinomas, Mohs achieves cure rates around 97%. These numbers are consistently higher than those for standard excision or destructive techniques.

How does reconstruction work after Mohs?

Once all cancer is removed, the Mohs surgeon may repair the wound themselves or refer you to a reconstructive specialist such as a facial plastic surgeon or oculoplastic surgeon for complex repairs, particularly around the eyelid or nose. The reconstruction plan depends on the wound’s size, depth, and location. Many wounds are repaired the same day; occasionally complex repairs are staged over more than one visit.

Trusted Resources

• American Academy of Dermatology – Mohs Surgery
• Skin Cancer Foundation – Mohs Surgery
• Mayo Clinic – Mohs Surgery
• American College of Mohs Surgery – Patient Information

Always consult a board-certified dermatologist or Mohs surgeon for diagnosis and treatment recommendations specific to your situation.