Your Mohs Surgery Day: A Step-by-Step Walkthrough

Why Mohs Surgery Takes All Day

Patients are often surprised to learn that Mohs surgery is not like a regular biopsy where you are in and out in 20 minutes. The reason it takes longer is also what makes it so effective: between each stage of removal, the surgeon personally reviews 100% of the tissue margins under a microscope. This on-the-spot pathology is what allows Mohs to achieve cure rates of 98–99% for common skin cancers.

Plan to be at the office for the full day — typically 4–8 hours, though you may leave sooner. Bring something to keep yourself occupied during the waiting periods between stages: a book, a tablet, headphones, or a friend to keep you company. Eat a light breakfast before you arrive unless told otherwise.

What to Do Before You Arrive

Your care team will give you specific instructions. General preparation usually includes:

• Take your usual morning medications unless told to hold blood thinners
• Eat breakfast — you will be there a long time and need energy
• Wash the area to be treated with mild soap; do not apply lotion or makeup to it
• Wear comfortable, loose-fitting clothing appropriate for the location being treated
• Arrange a ride home if the treatment site is near your eye or if you will be anxious after surgery
• Avoid alcohol for 24 hours before the procedure

If you take aspirin, warfarin, clopidogrel, or other blood-thinning medications, ask your doctor whether to continue them. Most Mohs surgeons prefer you stay on blood thinners to reduce clotting risks, but your specific situation may differ.

When You Arrive: Check-In and Setup

After check-in, a nurse or medical assistant reviews your health history, takes photos of the site, and asks about allergies — especially to anesthetics. You will be positioned comfortably in a procedure chair or table. The skin around your cancer is cleaned with an antiseptic solution and draped with sterile material.

Step 1: Local Anesthesia

The surgeon injects local anesthesia — typically 1% lidocaine with epinephrine — around the tumor site. The injection stings for 10–30 seconds and is usually the most uncomfortable part of the whole procedure. Once the area is numb (which takes 5–10 minutes), you should feel no pain. You will feel pressure and movement, but not sharp pain. If you feel anything sharp during the procedure, let your doctor know immediately.

The epinephrine in the anesthetic also causes blood vessels to constrict, which minimizes bleeding and keeps the surgical field clear.

Step 2: First Stage of Removal

The surgeon removes the visible tumor along with a thin margin of surrounding tissue — typically 1–2 mm. This margin is much smaller than a standard excision, which is how Mohs conserves normal tissue. The removed tissue (called a "layer" or "stage") is carefully mapped: it is divided into sections, each marked with colored dyes at precise locations, so the surgeon can later pinpoint exactly where cancer cells are, if any remain.

A temporary dressing is placed over your wound. You will then wait — usually 45 minutes to 1.5 hours — while the tissue is processed in the on-site laboratory.

The Wait: What Is Happening in the Lab

This waiting time is what makes Mohs different from any other skin cancer surgery. While you sit in the waiting room, the surgeon (who is also the pathologist) is in the lab preparing the tissue slides, staining them, and examining the entire undersurface and edges of the removed layer under a microscope. This is called frozen section histology.

If no cancer cells are found at any of the margins, you are clear and reconstruction can begin. If cancer cells are seen at a specific margin, that location is identified on the map, and only that section needs to be re-excised in the next stage.

Step 3 and Beyond: Additional Stages

If more tissue needs to be removed, the surgeon re-numbs only the affected area and removes another thin layer precisely where the cancer was found. That layer goes back to the lab. The process repeats until all margins are completely clear. About 70% of Mohs cases are cleared in one stage. Most of the remaining 30% require two or three stages. Rarely are more than three stages needed.

Step 4: Wound Reconstruction

Once the wound is confirmed cancer-free, your surgeon discusses repair options with you. The approach depends on the size and location of the wound:

• Simple stitches (linear closure): For smaller wounds with enough surrounding skin
• Flap repair: Nearby skin is slid or rotated to cover the wound — common on the nose, cheeks, and scalp
• Skin graft: A thin piece of skin from another area (often behind the ear or inner upper arm) is used to cover the wound
• Second-intention healing: For some locations, allowing the wound to heal naturally without stitches gives excellent cosmetic results

The repair can take 30 minutes to over an hour depending on complexity. For large or intricate areas (like the eyelid or nose), a plastic surgeon or oculoplastic specialist may perform the reconstruction — sometimes on the same day, sometimes at a follow-up visit.

Going Home: Aftercare Instructions

Most patients drive themselves home after simple Mohs procedures; however, if your surgery is near your eye, or if you feel lightheaded or anxious, having a driver is wise. Before you leave, the nursing staff will review wound care instructions:

• Keep the wound covered with a bandage for the first 24–48 hours
• Clean gently with mild soap and water, then apply a thin layer of petroleum jelly (Vaseline) to keep the wound moist — this helps healing and reduces scarring
• Avoid strenuous activity for 1–2 weeks to prevent bleeding or wound reopening
• Expect some swelling, bruising, and mild discomfort for a few days — over-the-counter acetaminophen is usually enough
• Do not soak the wound (no swimming or hot tubs) until fully healed

You will be scheduled for a follow-up visit to check healing and remove sutures (usually 1–2 weeks after surgery). Long-term follow-up appointments are also recommended because people who have had one skin cancer have a higher chance of developing another.

When to Call the Office or Seek Urgent Care

• Bleeding that does not stop with 15–20 minutes of firm pressure
• Increasing pain, redness, warmth, or drainage from the wound after the first 48 hours (possible infection)
• Fever over 101°F (38.3°C)
• Wound edges separating or stitches breaking
• Numbness or weakness beyond what was expected

Frequently Asked Questions

Will I be awake during Mohs surgery?

Yes. Mohs surgery is performed under local anesthesia, so you are awake but the surgical area is completely numb. General anesthesia is not needed and is rarely used. Most patients find the procedure much less intimidating than they expected once the initial injection is done.

Can I eat and drink the day of surgery?

Yes — in fact, you should. Eat a normal breakfast before you arrive. You will likely be there for several hours, and having food in your system helps prevent lightheadedness. You can bring snacks and a drink for the waiting periods between stages.

How much will it hurt afterward?

Most patients describe the soreness as mild to moderate — similar to a dental procedure. Over-the-counter acetaminophen manages it well for most people. Avoid ibuprofen and aspirin for the first 24 hours as they can increase bleeding risk. The discomfort typically peaks on day 2–3 and improves steadily from there.

When will I see the final scar?

Scars continue to mature and soften for 12–18 months after surgery. What looks red and firm at 4 weeks will look much better at 6 months, and better still at one year. Your dermatologist can recommend treatments (silicone gel, sun protection, or in-office procedures) to optimize the final result.

Trusted Resources

• American Academy of Dermatology — aad.org
• American College of Mohs Surgery — mohscollege.org
• Skin Cancer Foundation — skincancer.org
• Mayo Clinic — mayoclinic.org

Always consult a board-certified dermatologist for personalized medical advice about your skin cancer treatment options.