Key takeaways
- Mohs surgery removes skin cancer in thin layers and checks the edges under the microscope while you wait.
- It's used mainly for higher-risk basal and squamous cell carcinomas and for sensitive areas such as the face, ears, hands and genitals.
- Cure rates reach up to 99% for skin cancers that haven't been treated before.
- Plan for several hours, and ask in advance about driving, medicines and wound care.
What Mohs surgery is
Mohs micrographic surgery is a way of removing skin cancer one thin layer at a time. The surgeon removes the visible tumor and a thin rim of tissue around it. That layer is mapped, color-coded and processed in the office lab, and the surgeon reads its edges under the microscope while you wait. If cancer cells remain anywhere along the edge, the map shows exactly where, and only that spot is treated again. The process repeats until no cancer is seen.1
Two things set Mohs apart. The edges are checked during the visit, not days later. And because extra tissue is only taken where the cancer is, as much healthy skin as possible is spared. That matters on the nose, eyelids, lips and ears, where every millimeter counts.12
Who it's for
Mohs isn't necessary for every skin cancer. The American Academy of Dermatology, the American College of Mohs Surgery and other societies published appropriate use criteria to help decide when Mohs is the right tool. They weigh the tumor's location, size and subtype, whether it has come back after earlier treatment, and the person's health, including a weakened immune system.3
In practice, Mohs is most often used for:
- basal and squamous cell carcinomas on the face, ears, scalp, hands, feet and genitals
- tumors with aggressive features under the microscope, or with edges that are hard to see
- skin cancers that have come back after earlier treatment
- people whose immune systems are suppressed, for example after an organ transplant
The AAD guidelines for basal cell and squamous cell carcinoma recommend Mohs surgery for high-risk tumors. They also recognize standard excision and other approaches as effective for many low-risk tumors, such as a small basal cell carcinoma on the back.45
Before the day
- Medicines. Tell the office about every medicine and supplement, especially blood thinners. Don't stop a prescribed blood thinner unless the doctor who prescribed it tells you to.
- Time. Clear most of the day. You may spend much of it in a waiting area between layers.
- Comfort. Eat breakfast, bring a book or something to do, and wear comfortable clothes.
- Getting home. Ask whether you'll need a driver. Bandages near the eye can make driving unsafe.
On the day, layer by layer
The area is numbed with a local anesthetic, and you stay awake. If the cancer is on your face, you probably won't see what's happening, but the surgeon will tell you each step.1
- The visible tumor and a thin first layer are removed, and a temporary bandage goes on.
- The tissue is mapped, frozen, cut into very thin sections and stained in the lab.
- The surgeon examines every edge under the microscope.
- If cancer remains, you're numbed again and a small extra layer is taken only from that spot.
- When the edges are clear, the wound is repaired.
Many tumors are cleared in one or two layers. If more are needed, the visit can take several hours.1
Repairing the wound
Once the edges are clear, the surgeon plans the repair. Depending on the size and location of the wound, the options are:1
- Healing on its own (called second-intention healing), which can leave a very good result in some places, such as concave areas of the face. Dr. Nathan has published on techniques that help these wounds heal well.
- Stitches in a line, which is the most common repair.
- A flap, which moves nearby skin into the wound.
- A graft, which takes skin from another site.
Most repairs are done the same day. Occasionally, the Mohs surgeon works with a plastic, oculoplastic or hand surgeon.1
Healing and what comes next
Expect some swelling and bruising for several days, especially around the eyes. Follow your written wound-care instructions, and rest the area from heavy activity as advised. Scars keep improving for many months.
A first skin cancer is a reason for regular checks. People who have had basal cell carcinoma are at higher risk of another one, and the AAD guideline advises at least yearly skin exams after treatment.4
When to see a doctor
Contact the office the same day if bleeding doesn't stop after 20 minutes of firm pressure, or if you notice spreading redness, warmth, pus or fever. For heavy bleeding that won't stop, or trouble breathing, call 911.
Sources
- The Skin Cancer Foundation. Mohs Surgery. Updated October 2025. View source (opens in a new tab)
- American College of Mohs Surgery. About Mohs Surgery (for patients). View source (opens in a new tab)
- Connolly SM, Baker DR, Coldiron BM, et al. AAD/ACMS/ASDSA/ASMS 2012 appropriate use criteria for Mohs micrographic surgery. J Am Acad Dermatol. 2012;67(4):531-550. doi:10.1016/j.jaad.2012.06.009 View source (opens in a new tab)
- Work Group; Invited Reviewers; Kim JYS, Kozlow JH, Mittal B, et al. Guidelines of care for the management of basal cell carcinoma. J Am Acad Dermatol. 2018;78(3):540-559. doi:10.1016/j.jaad.2017.10.006 View source (opens in a new tab)
- Work Group; Invited Reviewers; Alam M, Armstrong A, Baum C, et al. Guidelines of care for the management of cutaneous squamous cell carcinoma. J Am Acad Dermatol. 2018;78(3):560-578. doi:10.1016/j.jaad.2017.10.007 View source (opens in a new tab)
This article is general education for adults and isn't a substitute for personal medical advice. In an emergency, call 911.