Mohs Surgery

What is Mohs surgery?

Mohs surgery (also called Mohs micrographic surgery) is a specialized way of removing skin cancer one thin layer at a time. After each layer is removed, it is examined under a microscope while you wait. The surgeon keeps removing tissue only from the spots where cancer cells are still seen, and stops as soon as the edges are clear. The goal is to take out all of the cancer while sparing as much healthy skin as possible.

The technique is named after Dr. Frederic Mohs, who developed it in the 1930s. Today it is a standard treatment for certain skin cancers, and it is usually performed by a dermatologist (a doctor who specializes in skin conditions) who has completed additional training in Mohs surgery and in reading tissue under the microscope.

Mohs surgery is used most often for the two most common types of skin cancer:

• Basal cell carcinoma (BCC), a slow-growing cancer that starts in the basal cells at the bottom of the outer skin layer.
• Squamous cell carcinoma (SCC), a cancer that starts in the flat squamous cells nearer the skin surface and can, in some cases, spread if left untreated.

It is sometimes also used for certain less common skin tumors and, in selected cases, for some forms of melanoma (a cancer of the pigment-producing cells), although melanoma is more often treated with other surgical approaches. Your care team will explain which type of skin cancer you have and why a particular treatment is being suggested.

Who needs Mohs surgery: candidates and exceptions

Not every skin cancer needs Mohs surgery. Many small, low-risk skin cancers can be treated well with a simpler procedure, such as standard excision (cutting out the growth with a margin of normal skin) or curettage (scraping) followed by cautery. Mohs surgery is generally reserved for situations where saving healthy tissue or achieving complete removal is especially important. Common reasons a doctor may recommend it include:

• The cancer is on the face, ears, nose, lips, eyelids, scalp, hands, feet or genitals, where there is little spare skin and appearance or function matters greatly.
• The cancer is large, or its edges are hard to see with the naked eye.
• The cancer has grown back after an earlier treatment.
• The cancer is an aggressive subtype, or it is growing quickly.
• The cancer is in scar tissue or in an area that was previously treated with radiation.
• You have a weakened immune system, for example after an organ transplant, which can make skin cancers behave more aggressively.

Mohs surgery may not be the best choice when the cancer is small and low-risk in an area such as the trunk, where a standard excision can work just as well with less time in the clinic. It is also generally not used for cancers that have already spread to lymph nodes or other organs, because those situations need a broader treatment plan that may include other surgery, radiation therapy or medication. People who cannot tolerate lying still for a long appointment, or who cannot safely stop or manage certain medications, may be offered alternatives. Your dermatologist will weigh these factors with you.

How the Mohs surgery procedure works

The Mohs surgery procedure is almost always done in an outpatient setting, meaning you go home the same day. It is performed under local anesthesia (numbing medicine injected into the skin), so you are awake but should not feel pain in the area. The steps below describe what typically happens.

Before the procedure

You will usually have already had a biopsy (a small sample of the growth removed and examined) that confirmed the diagnosis. On the day of surgery, the team will clean the area, mark the visible edges of the cancer, and inject the numbing medicine. The injection stings briefly, and then the area becomes numb.

During the procedure

• Removing the first layer. The surgeon removes the visible tumor along with a thin rim of surrounding tissue. A temporary dressing is placed over the wound.
• Mapping and processing. The removed tissue is marked with colored dyes so it can be matched precisely to its position on your skin. It is then frozen, cut into very thin slices, stained and placed on glass slides. This step often takes an hour or more.
• Microscopic examination. The Mohs surgeon examines the entire edge and undersurface of the tissue. If cancer cells are found, their exact location is noted on the map.
• Additional stages if needed. The surgeon numbs the area again if necessary and removes another thin layer only from the spot where cancer remains. This cycle repeats until no cancer cells are seen. Many patients need one to three stages, but more are sometimes required.
• Repairing the wound. Once the area is clear, the surgeon discusses how to close the wound. Options include allowing it to heal on its own, closing it with stitches, moving nearby skin to cover the area (a flap), or using a piece of skin taken from elsewhere on your body (a graft). Occasionally the repair is done by another surgeon or on a later day.

After the procedure

A pressure dressing is applied, and you are given written instructions on wound care, pain control and warning signs. Because only local anesthesia is used, many people are able to travel home on their own, although having someone with you is often recommended if the surgery is near the eye or if you feel lightheaded.

Preparation for Mohs surgery

Preparation is mostly about safety and comfort. Your team will give you specific instructions, which may include the following.

• Review your medications. Tell your doctor about all prescription and over-the-counter medicines and supplements, especially blood thinners, aspirin and anti-inflammatory drugs. Do not stop any prescribed medication on your own; some blood thinners should be continued because stopping them carries its own risks.
• Mention health conditions. Let the team know about allergies, a pacemaker or other implanted device, bleeding disorders, a history of infections in surgical wounds, or artificial joints or heart valves, since some of these may change the plan.
• Eat a normal breakfast. Because only local anesthesia is used, you can usually eat and drink as normal unless told otherwise. Bringing a snack and something to read is sensible, as the day can be long.
• Avoid alcohol and smoking. Alcohol can increase bleeding, and smoking slows wound healing. Your doctor may ask you to limit both before and after surgery.
• Plan your day. Wear comfortable, loose clothing that will not rub the surgical area. Clear your schedule for the whole day, and arrange transport if the surgery is near your eyes or if you tend to feel faint.

Mohs surgery recovery time and aftercare

Mohs surgery recovery time varies with the size and location of the wound and how it was repaired. The following timeline is typical, but your own experience may differ.

• First 24 to 48 hours. Mild soreness, swelling and some bruising are common, especially around the eyes and forehead. Keeping the area elevated and applying a cold pack over the dressing (if allowed) can help. Most discomfort responds to simple pain relievers your doctor approves.
• First week. You will usually keep the original dressing on for a day or two, then begin gentle cleaning and applying an ointment as instructed. Many patients return to desk work within a day or two. Heavy lifting, bending and vigorous exercise are often restricted for one to two weeks to reduce bleeding and strain on the stitches.
• One to three weeks. Stitches, if used, are typically removed within about one to two weeks, depending on the site. Wounds left to heal on their own may take several weeks to close.
• Several months. Scars usually look red or raised at first and then soften and fade over many months. Numbness or tightness around the site is common and often improves gradually, though it can occasionally persist.

General aftercare advice often includes keeping the wound clean and covered as directed, avoiding soaking it in baths or pools until cleared, protecting the scar from sun exposure, and not picking at scabs. Follow-up visits allow your doctor to check healing and, later, to monitor your skin for new or returning cancers. In an integrated hospital system such as Acibadem, Mohs surgery is generally coordinated through the Dermatology department, which also handles routine skin checks afterward.

Mohs surgery risks and benefits: side effects to know

Understanding Mohs surgery risks and benefits helps you make an informed choice. The main benefit is that the surgeon checks all of the edges of the removed tissue during the same visit, which lets them remove the cancer completely while taking as little healthy skin as possible. This is why it is favored for cosmetically and functionally sensitive areas and for tumors that are likely to come back.

Like any surgery, Mohs surgery carries some risks. Serious complications are uncommon, but you should be aware of the following.

• Bleeding. Minor oozing is common in the first day. Heavier bleeding is less common and is more likely in people taking blood thinners.
• Infection. Signs include increasing redness, warmth, swelling, pus or fever. Antibiotics are sometimes needed.
• Pain and swelling. Usually mild and short-lived.
• Scarring. Every surgical wound leaves a scar. Its appearance depends on the size and site of the wound, the type of repair, your skin type and how you heal. Some scars may benefit from later revision or other treatments.
• Nerve effects. Small nerves in the skin are often cut, causing temporary numbness or tingling. Rarely, a nerve controlling muscle movement is affected, which can cause weakness in part of the face.
• Wound-healing problems. A flap or graft can occasionally fail to survive, particularly in smokers or people with poor circulation, and may need further treatment.
• Reaction to anesthesia. True allergy to local anesthetics is rare; a fast heartbeat or feeling shaky after the injection is more common and usually passes quickly.
• Incomplete removal or recurrence. Although Mohs surgery is designed to minimize this, no treatment can guarantee that a cancer will never return.

Results and outlook

The evidence generally shows that Mohs surgery offers among the highest cure rates of any treatment for basal cell and squamous cell carcinoma, both for tumors treated for the first time and for those that have come back after another treatment. Because the entire margin is examined, the chance that cancer cells are left behind is lower than with methods that check only a sample of the edges.

The outlook after treatment depends on several factors, including the type and subtype of the cancer, how large and deep it was, its location, whether it had been treated before and the state of your immune system. Squamous cell carcinomas that are large, deep or invading nerves carry a higher risk of returning or spreading than typical basal cell carcinomas, and your doctor may recommend closer follow-up or additional imaging in those cases.

Having had one skin cancer increases the likelihood of developing another in the future, either at the same site or elsewhere. For this reason, regular skin examinations, daily sun protection and self-checks for new or changing spots are considered an important part of long-term care rather than an optional extra.

Cost considerations

The cost of Mohs surgery differs widely between countries, health systems and clinics, so only general factors can be described here. Elements that commonly influence the overall price include:

• Number of stages. Each additional layer removed and examined adds surgeon and laboratory time.
• Type of wound repair. Simple closure is usually less involved than a flap or graft, and a repair performed by a separate reconstructive surgeon may be billed separately.
• Location and size of the tumor. Complex sites such as the nose, eyelids and lips often require more time and skill.
• Facility setting. An outpatient dermatology clinic and a hospital operating room have different overhead costs. Mohs surgery does not normally involve a hospital stay or implanted devices.
• Pathology and laboratory processing. The on-site preparation and reading of slides is a core part of the procedure.
• Follow-up care. Wound checks, stitch removal, scar treatments and long-term skin surveillance may be charged separately.
• Insurance coverage. Many insurers cover Mohs surgery when it is medically indicated, but out-of-pocket amounts vary. Asking for a written estimate in advance is reasonable.

Frequently asked questions

Is Mohs surgery painful?

The procedure itself is performed under local anesthesia, so most people feel pressure or tugging but not sharp pain. The initial numbing injection stings for a few seconds. Afterward, soreness is usually mild and is often managed with acetaminophen or another pain reliever your doctor recommends. Pain that worsens rather than improves over the first days should be reported.

How long does the Mohs surgery procedure take?

Most of the time is spent waiting while each layer of tissue is processed and examined. Many patients are in the clinic for about two to four hours, but appointments can run longer if several stages are needed or if the wound repair is complex. It is best to plan for the whole day and to bring something to occupy the waiting periods.

What is the typical Mohs surgery recovery time?

Many people return to light daily activities and desk work within one to two days. Strenuous exercise and heavy lifting are commonly restricted for one to two weeks to protect the wound. Stitches are typically removed within one to two weeks, and scars continue to fade and soften over several months to a year. Larger wounds and those repaired with flaps or grafts generally take longer.

Who needs Mohs surgery instead of a standard excision?

Mohs surgery is usually recommended when a skin cancer is on the face or another area where sparing tissue matters, when it is large or has unclear borders, when it has returned after previous treatment, when it is an aggressive subtype, or when the patient has a weakened immune system. Small, low-risk cancers on the trunk or limbs can often be treated effectively with simpler methods. Your dermatologist will explain which approach fits your situation.

What are the main Mohs surgery risks and benefits compared with other treatments?

The key benefit is complete examination of the tissue margins during a single visit, which supports both high cure rates and minimal removal of healthy skin. Risks are similar to other skin surgeries and include bleeding, infection, scarring and temporary numbness; serious complications are uncommon. Radiation therapy and topical treatments are alternatives for some patients, each with its own trade-offs that your doctor can discuss.

Will Mohs surgery leave a scar?

Yes, any surgery that goes through the full thickness of the skin leaves a scar. Because Mohs surgery removes as little healthy tissue as possible and because the repair is planned carefully, scars are often smaller than they would otherwise be. Scars generally look most noticeable in the first weeks and improve over months. If a scar remains bothersome, treatments such as silicone products, injections or laser therapy may be discussed later.

Can skin cancer come back after Mohs surgery?

Recurrence is uncommon after Mohs surgery, but no treatment can offer a guarantee. In addition, people who have had one skin cancer are more likely to develop new ones at other sites. Regular follow-up skin checks and consistent sun protection are recommended for this reason.

When to see a doctor

You should have any new or changing skin growth assessed by a dermatologist, particularly a spot that is a sore that does not heal within a few weeks, a shiny or pearly bump, a scaly or crusted patch that bleeds easily, a growth that changes in size, shape or color, or a mole that looks different from your others. People with fair skin, a history of heavy sun exposure or sunburns, previous skin cancer, or a weakened immune system benefit from routine skin examinations even without symptoms.

After Mohs surgery, seek prompt medical attention if you notice any of the following:

• Bleeding that does not stop after 20 minutes of firm, steady pressure.
• Spreading redness, warmth, increasing swelling, pus or a foul smell from the wound.
• Fever or chills.
• Pain that becomes worse rather than better after the first day or two.
• The wound edges pulling apart or a skin graft turning dark.
• New weakness in facial movement, or sudden vision changes after surgery near the eye.
• Signs of an allergic reaction, such as a widespread rash, hives or difficulty breathing, which require emergency care.

In the months and years that follow, contact your dermatologist if you see a lump, bump or non-healing area developing at or near the surgical scar, since this can be an early sign of a returning cancer and is easier to treat when found early.