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When Mohs Surgery Doesn't Go As Planned: Understanding the Risks and Complications

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How to Spot a Botched Mohs Surgery: Recognizing the Red Flags

Mohs surgery is considered the gold standard treatment for certain types of skin cancer.

With its extremely high cure rate of up to 99%, it's easy to assume that complications from Mohs surgery are rare.

However, while major issues are uncommon, patients should still be aware of the potential risks and side effects of this procedure.

By understanding the possible complications of Mohs surgery, patients can take steps to minimize risks and be prepared if any problems do arise during or after the surgery.

What Is Mohs Surgery and Why Is It Used?

Mohs surgery, named after Dr. Frederic E. Mohs who developed the technique in 1938, involves surgically removing skin cancer layer by layer.

After each layer is removed, the tissue is immediately examined under a microscope. This process continues until only cancer-free tissue remains.

This precise, systematic approach helps ensure all cancer cells are eliminated while preserving as much healthy tissue as possible.

Mohs has the highest cure rate of any skin cancer treatment and results in the smallest possible wound needed to remove the tumor. It is useful for cancer in delicate areas like the face.

What Are Some Common Complications From Mohs Surgery?

While major complications are rare, some minor issues can occur. Common side effects and risks include:


Some minor bleeding is expected after the procedure. However, uncontrolled or excessive bleeding is possible if blood vessels are inadvertently damaged during the surgery. Applying pressure to the wound for 10-15 minutes after surgery can usually stop minor bleeding.


Infection rates for Mohs surgery are typically quite low (1-2%). However, any surgical site involves some infection risk. Signs include increasing pain, swelling, redness, warmth, and pus-like drainage from the wound. Infections usually respond well to oral or topical antibiotics.

Poor Wound Healing

For wounds to heal properly, the skin edges must be brought together neatly. This may not always be feasible based on the wound's location and size. Large, deep, or poorly aligned wounds can result in scarring or require reconstructive surgery with flaps or grafts.


Scarring of some degree occurs with all surgeries. Mohs often produces minimal scarring since it preserves the greatest amount of healthy tissue. However, poor wound healing can lead to larger, thicker, or more visible scars. Scars may fade over one to two years.

What Are Some Rare But Serious Complications of Mohs Surgery?

While unlikely, there are some more serious complications that patients undergoing Mohs should be aware of:

Damage to Facial Nerves or Structures

Removing skin cancer from the face can potentially damage sensory nerves. In very rare cases, the nerves controlling facial muscles can be cut, resulting in facial paralysis or difficulty closing the eye. Surgery near the eyelid or lip can also distort these features.

Temporary or permanent facial numbness can be one of your signs. The lips, cheeks, chin, and nose are high-risk areas. Numbness usually fades over weeks or months but can persist in some minor cases.

Excessive Bleeding

While minor bleeding is common, uncontrolled hemorrhaging requires immediate medical attention. It can lead to anemia or cardiovascular complications. Excessive bleeding may result from clotting problems or damage to larger blood vessels.

Wound Dehiscence

Dehiscence refers to the surgical wound opening up after being closed with stitches or staples. Factors like infection, poor healing, and excessive tension on the closure can cause dehiscence. These wounds require immediate emergency care to prevent further expansion.

Osteonecrosis of the Jaw

This rare complication involves loss of blood supply to jaw bone, resulting in tissue death. It has been linked to some immunosuppressive medications patients may take after Mohs. While quite rare, it can lead to disfigurement and severely impact the quality of life.

New Cancer Growth at Surgery Site

The appearance of new cancer growth at the site of the original surgery is concerning.

Since Mohs surgery aims for the complete removal of cancer cells with narrow margins, any new growth could indicate the presence of residual cancer cells.

If symptoms such as itching, excessive bleeding, or numbing pain reemerge at the site of the original lesion, this could signal a recurrence of the cancer.

As Mohs surgery's objective is complete cancer removal, any returning symptoms warrant immediate medical evaluation.

How Do Patient Factors Influence Complication Risks?

Certain medical conditions and factors can increase a patient's risk of developing complications:

  • Age: Older patients may experience slower healing due to thinner skin, making them more susceptible to poor wound healing.
  • Diabetes: Diabetic patients often have impaired circulation and elevated blood sugar levels, which can hinder proper healing.
  • Immunosuppression: Those on immunosuppressive medication are at a higher risk for infections.
  • Blood Thinners: Use of anticoagulant medications can increase the risk of bleeding and impact wound healing.
  • Previous Radiation Treatment: Skin that has undergone radiation therapy is more fragile and less capable of healing efficiently.
  • Anatomical Location: Surgical sites on the face, ears, hands, and feet, which have less blood flow, may present higher surgical risks.
  • Skin Type: Individuals with darker skin may be more prone to hypertrophic scarring and keloid formation.
  • Tumor Size and Depth: Larger and deeper tumors are associated with a higher risk of complications post-surgery.
  • Delayed Reconstruction: Postponing the reconstruction of the surgical site can increase risks like infection and poor healing.
  • Individual Characteristics and Defect Features: These factors can necessitate additional procedures like skin grafts, influencing the overall risk profile.

Dermatology experts recommend patients with any of these risk factors discuss options to optimize healing before Mohs surgery. Steps like blood sugar control and stopping blood thinners under medical supervision can be taken to minimize risks.

How Can Patients Prepare for Surgery to Reduce Complications?

Patients should take certain steps prior to surgery to enhance healing and reduce risks:

  • Discuss health history thoroughly with your surgeon, including any conditions like diabetes or vulnerabilities like fragile skin. Be forthcoming about any medications you take.
  • Stop smoking for at least several weeks before and after surgery, as smoking impairs circulation and healing.
  • Closely follow pre-op directions from your surgeon, like avoiding blood thinners or adjusting medications.
  • Arrange for transportation to and from surgery, as well as assistance during recovery. You will likely be bandaged and unable to drive immediately after the procedure.
  • Set up follow-up check-ins with your surgeon to monitor for potential complications in the weeks following surgery. Be vigilant about attending all follow-ups.

Thorough preparation and open communication with your Mohs surgeon provide the best chance of avoiding complications like bleeding, scarring, infections, and poor wound healing.

What Is the Appropriate Post-Surgery Care and Monitoring?

Careful wound care and vigilance after surgery are crucial:

  • Take prescribed antibiotics to prevent infection unless otherwise directed by your surgeon.
  • Clean the wound site gently each day according to directions from your medical team. Avoid disturbing sutures or scabs.
  • Watch for signs of infection like worsening pain, swelling, redness, and pus-like drainage. Report any symptoms immediately.
  • Do not soak the wound in water from bathing, swimming, or hot tubs until given approval by your surgeon, as this raises infection risks.
  • Avoid sun exposure on healing or freshly healed scars for at least 6 months. Use SPF 30 or higher sunscreen on scars to prevent further sun damage.
  • Monitor your pain levels and notify your surgeon if you experience severe, worsening, or spreading pain, which could indicate complications.
  • Attend all scheduled follow-up visits so your care team can examine your progress and watch for any issues arising.

Strictly adhering to wound care instructions and reporting any concerns quickly leads to the best outcomes after Mohs surgery. Don't hesitate to call your surgeon with any questions or unexpected symptoms.

What Can Be Done to Treat Complications From Mohs Surgery?

If complications do develop, here are some common treatment approaches:

  • Infections are treated with oral or topical antibiotics. Occasionally, infected tissue may need to be drained or debrided.
  • Bleeding usually resolves with firm pressure on the wound for 10-15 minutes. Rarely, surgical intervention or cauterization may be required to seal damaged blood vessels.
  • Poor wound healing may involve allowing the wound to close on its own, using special dressings to optimize healing, or re-suturing the site. Severe cases may call for skin grafts or flaps.
  • Scarring can often be improved through prescription topical creams, silicone sheeting, laser therapy, steroid injections, or microneedling. In some instances, surgical scar revision may be performed.
  • Numbness typically diminishes over time as nerves regenerate. Physical therapy can help retrain facial muscles and reduce numbness duration.

Close monitoring and prompt treatment provide the best results when facing complications after Mohs surgery. Patients should follow up diligently with their care team.

When Is Scarring From Mohs Surgery Considered Severe Enough to Warrant Revision?

While some minimal scarring is expected with Mohs surgery, excessive or unaesthetic scarring may warrant scar revision procedures. According to dermatology experts, scarring severe enough to consider revision typically includes:

  • Hypertrophic or keloid scars that are red, thick, raised, and extend beyond the original wound borders
  • Scars with contour irregularities that significantly distort facial features and muscles
  • Scars restricting function and movement if located near joints, the eyes or the mouth
  • Scars wider than 3-4 mm for facial, neck, and hand regions
  • Scars exceeding 10-15 cm in length
  • Scars causing psychological distress due to their appearance and impact on self-image
  • Scars failing to improve in appearance after approximately one year of healing

Scarring requiring revision is evaluated on a case-by-case basis. Your Mohs surgeon can assess the need for revisions based on the scar’s physical characteristics and its functional and psychological effects.

What Surgical Options Exist for Revising Scars After Mohs Surgery?

If scar revision is deemed appropriate, some surgical techniques that may be used include:

  • Excision - surgically cutting out the scar and re-suturing in an improved direction
  • Z-plasty - reorienting the scar using z-shaped incisions to break up the straight line
  • W-plasty - making small, w-shaped cuts along the scar to minimize its size
  • Dermabrasion - using a rotating instrument to smooth the scar’s surface
  • Laser resurfacing - utilizing laser energy to minimize scar size and improve appearance
  • Filler injections - using dermal fillers like collagen to raise depressed scars
  • Flap surgery - moving nearby healthy skin to cover the defective scar area

The technique chosen depends on variables like scar size, depth, and location. Combinations of approaches may be used. Your surgeon will advise you on recommended options to optimize functional and cosmetic outcomes.

Conclusion: Preparation and Communication Are Key in Mohs Surgery

While certainly not guaranteed or even likely, patients considering Mohs surgery should have realistic expectations that complications can occasionally occur.

However, being informed of the risks and taking actions like quitting smoking, carefully following pre- and post-op directions, and promptly reporting concerns can greatly reduce the chances of complications arising.

Staying engaged with your treatment team and being vigilant in the recovery process allows for the best results from Mohs surgery.

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