Mohs Micrographic Surgery

Mohs Surgery is a complex procedure combining surgical excision with immediate microscopic examination of the entire tissue specimen margin by frozen tissue processing techniques right in the office while you wait. In addition to your physician, who serves as the Mohs surgeon and pathologist, histotechnologists are employed to process, cut, and stain the tissue specimen for proper histological study.

The four steps of Mohs surgery:

  1. Numbing the skin with a local anesthetic, marking the skin to create a map, and then surgical removal of a thin layer of skin containing the tumor in the shape of a pie.
  2. The specimen is color-coded and inked in the exact same orientation as a paper map that will be used during the microscopic examination.
  3. The tissue is frozen and sectioned into thin slices that are placed on glass slides and stained in the on-site Mohs laboratory.
  4. The Mohs surgeon examines the tissue slides under the microscope to determine if small residual tumor foci are left behind in the skin. The tissue is oriented on the slide so that the border of the tissue is examined. This allows your physician to examine 100% of the margin. If the tumor is removed completely, the skin defect is ready to be repaired. If the specimen is positive for residual tumor, steps 1 through 4 are repeated until there is no more tumor.

This detailed examination of 100% of the margin by Mohs Micrographic Surgery differs from all other pathology techniques. If you have a skin cancer removed by traditional excision, the tissue specimen will be sent to a pathology laboratory for processing and examination by a pathologist. The standard pathology techniques examine only 1% or less of the margin. If this 1% is clear of tumor, the pathologist and surgeon assume that the other 99% of the margin is also clear. The problem is that most complicated skin cancers grow in an unpredictable manner with tumor cells potentially wrapping around nerves or other deep structures. Therefore, even though a pathology report indicates clear margins, there may be tumor left behind on the 99% of the margin that was not examined. Mohs Micrographic Surgery has far fewer recurrences than standard excision because the entire margin is examined.

If there is residual cancer after the first Mohs stage, the Mohs Surgery technique allows your physician to pinpoint the exact location of the remaining tumor cells. This enables the surgeon to return to the treatment area and selectively remove another layer of skin from the cancer area only. This technique creates the smallest possible defect in the skin. Tumors treated by Mohs Surgery are often complex, and multiple stages are often required to clear the tumor. Examination of each of your stages takes up to 60 minutes. If multiple stages are taken, the Mohs procedure can take up a good percentage of the day. Most of this time will be spent sitting in the waiting room reading a book or magazine.

Advantages of Mohs Micrographic Surgery

  • Procedure performed by a dermatologic surgeon with special expertise in skin cancer
  • Highest rate of cure for skin cancer removal
  • Smallest amount of normal skin is removed, resulting in the smallest scar possible
  • Skin reconstruction is performed immediately
  • The entire procedure is performed under local anesthesia

How To Prepare For Your Surgery

  1. Do not take any aspirin or aspirin-containing products for at least 1 week prior to your surgery (unless prescribed by your Internist or Cardiologist). Aspirin thins the blood. Also, do not take other anti-inflammatory pills, like naproxen (Aleve), or ibuprofen. If your physician recommended that you take the aspirin, please check with him/her before stopping your medication. Please take Tylenol for a headache or pain. In addition, if you take supplemental Vitamin E or fish oil, please stop it at least 14 days before the procedure. Do not drink alcohol for 48 hours prior to surgery, as this also thins your blood.
  2. If you require antibiotic prophylaxis before dental procedures or other surgery, take your first dose of antibiotics 1 hour before coming to the office for your Mohs surgery. If you do not have a prescription at home, let us know when you are scheduled so we can call in your medication.
  3. If your skin cancer is located in the center of your face, eyelid, or eyebrow area where a bandage will block your vision or impact your ability to wear glasses, please have someone available to drive you to and from the office.
  4. Eat a normal breakfast or lunch on the day of surgery. Please bring a snack.
  5. Please wear comfortable clothing. Make sure that your shirt buttons in the front and does not slip over your head. No one-piece outfits. Bring a sweater or jacket, as the office can get cold on surgery days.
  6. Please take a shower and wash your hair on the morning of the day of surgery. Do not apply makeup (if the skin cancer is on your face), perfume, aftershave, or cologne.
  7. Take ALL your routine medications, as you normally would EXCEPT any of your medications that we have told you to stop.
  8. If you are unable to keep the scheduled appointment for surgery, please contact our office at least 48 hours in advance to reschedule your surgery appointment.

What To Expect On The Day Of Surgery

After you arrive in the office, one of our assistants will greet you and take you to the treatment room where the Mohs procedure will be performed. They will take your blood pressure and ask about your medications and allergies.
Your surgeon will be in to greet you before the start of the procedure and answer any last-minute questions. Please let us know if there is anything we can do to make you feel more comfortable (e.g. change the chair position).
First, your surgeon will numb the site with local anesthesia very similarly to a biopsy. This is the most uncomfortable part of the procedure. The numbing medication lasts a few hours, and if additional injections are needed later, these are usually painless or much less painful.

After the area is numb, your surgeon will remove a thin layer of skin affected by cancer. After the skin tissue is removed, an electric needle is used to stop any bleeding. The wound is bandaged and you will return to the waiting room. Over the next hour, your surgeon and the histotechnicians will process the tissue and examining the stained tissue sections with the microscope. Please be patient since this technique requires meticulous care.

If there is still skin cancer remaining, your surgeon will repeat the procedure as soon as possible. The average number of removals required is two to three stages. Fortunately, the Mohs procedure can be completed typically in less than a half-day and is on an outpatient basis.

Once your surgeon is confident that the skin cancer has been completely removed, he will discuss the options to repair the wound. Most often the wound can be closed in a linear fashion with stitches. This turns the circular hole in the skin into a fine straight line (scar). In other cases, a more complex procedure known as a flap or graft may be required to provide the best possible cosmetic result. This decision will depend on the wound size, depth, and location. If the wound is stitched up, the stitches are removed typically one week later, though this may vary from patient to patient.

The following video will explain the process in detail:


Wound Care Instructions After Mohs Micrographic Surgery

Supplies that need to be purchased prior to surgery:

  • Polysporin antibiotic ointment
  • Telfa dressing
  • Paper tape

All of these items are over-the-counter and are available in drug stores and pharmacies.


Keep the post-operative bandage in place until showering the next morning. Before showering, remove the bandage and discard it in the trash. Cleanse your incision with soap water (not hydrogen peroxide) to remove any drainage and crusting. Pat the wound dry and apply a generous layer of Polysporin ointment to the incision. Cover the Polysporin with a Telfa dressing cut into the shape of the wound. Tape the Telfa dressing in place with paper tape. Continue this wound care once daily until you return for suture removal.


Continue your regular medications as you normally would. Restart any medications stopped prior to surgery on the day after surgery. In the first 24 hours after surgery, take TYLENOL, not aspirin, for pain.


Spend the first-day post-surgery relaxing. Keep your head elevated during the first few evenings with a couple of pillows. If surgery was performed around the eyes, apply ice packs during the first 48 hours to minimize swelling. Antihistamines such as Zyrtec or Xyzal will be helpful in reducing swelling. Mohs surgeries performed on the forehead, cheek, or eyelid may result in a black eye. Heavy lifting and exercise are not allowed until after the sutures are removed. Showering can be started the morning after surgery. Pat the wound dry after leaving the shower and reapply the polysporin and bandage. Swimming is not allowed until after the sutures are removed.

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