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At Penn, our surgeons are experts in performing Mohs surgery for the removal of skin cancer. Mohs micrographic surgery combines a high cure rate with the sparing of healthy tissue for a better cosmetic and functional outcome.

What Is Mohs Surgery?

Mohs surgery is a highly skilled and precise surgical technique for the removal of various types of head and neck skin cancers including basal cell carcinoma, squamous cell carcinoma and melanoma. This type of surgery can also be used to remove rare or high-risk skin cancers that occur on the trunk and extremities. 

Mohs micrographic surgery offers the best chance for completely removing skin cancer while conserving as much healthy skin as possible. It uses microscopic guidance to decrease the likelihood of missing cancer cells not visible at the skin surface thus avoiding large incisions that unnecessarily remove healthy skin and result in bigger scars.

Mohs surgery offers those with skin cancer of the face, head or neck major advantages when undergoing this procedure including:

  • Immediate notification that the cancer is completely removed
  • The highest published cure rates for many forms of skin cancer, making it less likely that the cancer will recur
  • Cancer recurrence rates in patients who have had Mohs surgery is less than 2 percent, while those who do not undergo this surgery have recurrence rates of more than 10 percent
  • Maximum preservation of healthy skin for the best possible cosmetic and functional results

In most cases, patients undergo the reconstruction portion of their surgery on the same day as diagnosis and have procedures performed by the same Mohs surgeon.

Our state-of-the-art Mohs surgery unit is equipped with on-site laboratories that immediately process surgical specimens, allowing for real-time microscopic evaluation and immediate results to the patient.

About Penn's Mohs Surgeons

You can expect Penn’s dermatologic surgeons to handle all aspects of the Mohs procedure including:

  • Performing the surgery
  • Examining the excised microscopic cancerous lesion or tumor in the on-site laboratory
  • Performing the reconstructive surgery

While many community-based dermatologists and primary care doctors counsel their patients in advance about the Mohs surgical process, Penn's dermatologic surgeons meet with and evaluate patients prior to surgery to discuss any pre-operative concerns related to skin cancer and its treatment.

Evaluation procedures include counseling patients on the surgical process — this communication puts patients and their families at ease prior to surgery. During the evaluation phase, patients learn about the procedure and the benefits of undergoing Mohs surgery at Penn.

How to Prepare for Mohs Surgery and Reconstruction

Patients should review all pre-treatment instructions with their physician prior to undergoing Mohs surgery and reconstruction. Penn's Mohs surgeons are available for consultation or questions prior to surgery.

Prescription Medications

Before surgery, it is not necessary to stop medications prescribed or ordered by primary care or other physicians, including blood thinners.

Patients should bring a complete list of their medications on the day of the scheduled surgeries.

Patients that take Coumadin® (warfarin) should have a routine blood study (PT/INR) drawn no more than one week before the Mohs surgery appointment and notify Penn Dermatology with the results prior to surgery. The results can be faxed to the office where the Mohs procedure is being performed or contact the office with the name and contact information of the facility that performed the blood study so the Penn Dermatology staff can obtain the results directly. The fax number is 215-662-4132.

Over-the-Counter or Supplemental Medications

Stop taking all medications not prescribed by a doctor or referring physician for protection from potential bleeding complications seven to 10 days prior to surgery including:

  • Aspirin
  • Ibuprofen (e.g., Motrin®, Advil®)
  • Vitamin E
  • Nutritional or health-food supplements

Refrain from drinking alcoholic beverages three days prior to the surgery and three days after the surgery since alcohol increases the risk of bleeding.


Antibiotics are usually not prescribed prior to Mohs surgery. However, Penn Dermatology recommends antibiotics 30 to 60 minutes prior to the surgery for patients that have had:

  • Joint replacement surgery within the past year
  • Artificial heart or heart valves
  • History of endocarditis/infected heart valves
  • Severe dysfunction of a heart valve

Patients that qualify for any of these medical situations should call the office where the surgical procedure will be performed two to three days before the Mohs surgery appointment so an appropriate antibiotic can be prescribed.

Eating Before Surgery

Patients should eat a normal breakfast prior to arriving for surgery. If the surgery requires several stages, patients can eat a snack or lunch during the day. Patients may also pack a lunch or bring snacks.

What To Expect

Patients should review all surgical treatment information with their physician prior to undergoing treatment for Mohs surgery and reconstruction. Penn Dermatology's Mohs surgeons are available for consultation or questions at any time during the entire treatment process.

During Mohs surgery, patients may experience minor discomfort when local anesthesia is injected around the skin cancer. The discomfort is similar to the biopsy that was done for their skin cancer.

After numbing the area around the skin cancer, the Mohs surgeon removes all visible portions of the skin cancer and a thin margin of normal-appearing skin. A staff member places a temporary bandage over the wound and takes the patient to a waiting area. While the patient waits, the Mohs surgeon examines the entire edge of the removed skin under the microscope in Penn Dermatology's on-site laboratory.

Patients do not feel pain while the Penn Mohs surgeon removes the skin cancer or stitches the wound. Subsequent anesthetic injections prior to any additional stages or reconstruction of the wound are often painless, since the anesthesia from the first injection is usually still effective.

If microscopic examination shows that the cancer has been completely removed, the wound is ready to be repaired. But if microscopic examination identifies extensions of the cancer that are not visible at the surface of the patient's skin, the Mohs surgeon needs to remove those precise areas where the cancer still remains.

If all of the cancer was not removed in the previous stage, the staff member brings the patient back to the operating room. During subsequent stages, the Mohs surgeon cuts out the precise areas where cancer still remains. The process of targeted cancer removal and complete microscopic margin examination continues until the Mohs surgeon finds that all of the cancer has been removed.

When all of the cancer has been removed, the Mohs surgeon discusses all the options for repairing the wound with the patient.

How Long Does Mohs Surgery Take?

The Penn Mohs surgical team cannot predict precisely how long it takes to remove the skin cancer and reconstruct the surgical wound. Times vary depending upon the nature and characteristics of the skin cancer. It is strongly recommended that patients plan to spend the entire day at Penn Dermatology and cancel any other appointments on the day of their surgery.

Waiting is the most difficult part of the process. The dermatology staff strives to keep patients informed of their progress and work efficiently so patients can return to the comfort of their homes as quickly as possible. It is recommended to bring reading materials or a companion to help pass the time.

In most cases, the Mohs surgeon repairs the final surgical wound the same day of surgery after confirming that all of the cancer has been removed. Most wounds are repaired with stitches. Patients that cannot tolerate reconstruction on the same day of surgery or whose wounds are extensive and inappropriate for reconstruction under local anesthesia are rescheduled to return for reconstructive surgery.

Scarring and Healing after Mohs Surgery

In most cases, the Mohs surgeon immediately repairs the wound with stitches. Larger wounds may require a flap by rearranging skin from near the wound, or a graft that borrows skin from another site to cover the wound. In certain cases, the surgeon may recommend letting the wound heal on its own to achieve the best appearance.

Any surgery to remove skin cancer results in a scar. However, the precision of the Mohs technique helps decrease the amount of scarring by removing all of the diseased skin while leaving behind as much healthy skin as possible. Penn Dermatology's Mohs surgeons are skilled in surgical reconstruction and repair wounds to minimize the scar as much as possible.

Most patients heal well and do not require additional treatment to their scars. However, patients with concerns about the scarring or healing process should contact Penn Dermatology to discuss other options for cosmetic improvement.

Returning Home

Mohs surgery is performed under local anesthesia. Patients return home with a bandage over the surgical wound. In rare cases, hospitalization may be necessary, in which case Penn Dermatology makes the hospital admission arrangements for patients.

Penn Dermatology recommends that a companion drives patients home after surgery. Postoperative swelling or bulky dressings used to cover the surgical wound may obstruct vision or restrict movements, making driving alone dangerous. Driving is prohibited if a sedative is administered during surgery for nerves or anxiety.

Risks and Outcomes

You should review all pre- and post-surgical information with your physician before and after Mohs micrographic surgery and reconstruction. Our Mohs surgeons are available for consultation or questions regarding all aspects of the procedure, including post-treatment.

Instructions After Mohs Surgery for Skin Cancer

Post-treatment care and instructions after Mohs surgery includes the following:

Pain or Discomfort

Most patients have minimal pain after Mohs surgery that is usually controlled by taking acetaminophen (Tylenol®). You should avoid products containing aspirin or ibuprofen as these can promote bleeding. In some cases, the surgeon may prescribe a stronger medication for pain.

Wound Care

Our clinical staff will explain and demonstrate the techniques for wound care immediately after Mohs surgery. You will also receive written instructions and information for contacting your Penn Mohs surgeon directly, in the rare case of an emergency.

In order to protect the surgical wound, you should avoid strenuous activities for at least one week after surgery. You should prepare for the possibility of visible swelling, redness and bruising for one or two weeks after surgery, especially if the skin cancer is on the central face (forehead, eyes, nose or lips).

Scarring and Healing

Any surgery to remove skin cancer results in a scar. However, the precision of the Mohs technique helps decrease the amount of scarring by removing all of the diseased skin while leaving behind as much healthy skin as possible. Our expert Mohs surgeons repair surgical wounds to make the scar as minimal and unnoticeable as possible.

Most patients heal well and do not require additional treatment for their scars. However, if you have concerns about the scarring or healing process, you should contact Penn Dermatology to discuss other options for cosmetic improvements.

Follow-up Care

Patients usually return in one to two weeks to have their stitches removed and to ensure that the wound is healing well. You may need to return for additional visits to ensure that the scar has healed with the best possible result. It is important for you to return regularly to your referring doctor or primary care provider for regular skin checkups to look for any new skin cancers.

Skin Cancer Recurrence Rates after Mohs Surgery

Approximately 1 to 2 percent of skin cancers may grow back after Mohs micrographic surgery. For certain high-risk skin cancers, this recurrence rate may be higher.

Since there is a slim chance the skin cancer may grow back, we recommend consistent monitoring of the surgical site, as well as all other areas of the body for any signs of skin cancer. You should contact Penn Dermatology or the referring health care provider for evaluation if they have any concerns that the skin cancer may be growing back.

Adopting Sun Smart Habits

Adopting sun-smart habits and performing regular self-skin examinations are critical to keeping skin healthy and cancer free.

We recommend that all patients adopt these sun-smart habits including:

  • Faithful avoidance of harmful ultraviolet (UV) rays from the sun (or from tanning salons), especially between the peak hours of 10 am to 4 pm
  • Sensible coverage with clothing, including a broad-brimmed hat, long sleeves and pants, whenever possible
  • Daily use of a broad-spectrum sunscreen (UVA/UVB protection) with a sun protection factor (SPF) of 30 or higher on areas of exposed skin
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