Mohs Surgery and Its Indications

In his session, “Understanding Mohs Surgery and Its Indications,” presented at Dermatology Week 2022, Howard Steinman, MD, discussed the principles and indications of Mohs surgery, along with the necessary clinical information and newer fast-acting immunohistochemistry (IHC) stains for squamous cell carcinoma (SCC) and melanoma.

After a brief history of Mohs surgery, Dr Steinman started with Mohs surgery technique. Some of the essential aspects he mentioned are:

• Excise specimens so the complete margins can be flattened.
• Transfer the specimen to the laboratory maintaining orientation.
• Create a Mohs map of the wound shape and reference nicks/marks.
• Record specimen inking/subdivisions on the map.
• Prepare frozen-section pathology slides.
• Examine the slides for areas requiring further surgery.
• Draw these areas precisely on the map.
• Correlate map findings with wounds to remove more tissue.

He noted that the pathology evaluation must be performed by the surgeon and cannot be delegated in Mohs surgery.

Dr Steinman also went over the advantages of Mohs surgery, such as it has the highest cure rates for nearly all skin types, fast pathology results, and cost effectiveness with insurance. The disadvantages of Mohs surgery include the challenges of extended time in the office and the cost if the patient is not insured.

As for the indications for Mohs surgery, Dr Steinman suggested looking into the National Comprehensive Cancer Network (NCCN) as “it is thoroughly evidence-based, has algorithmic guidelines, is frequently updated (every 2 years), and provides treatment options for each type of tumor.” He mentioned the following criteria as the evidence-based Mohs surgery indications:

• Size: greater than 2 cm
  • High risk of subclinical spread, tissue destruction, and/or deep invasion.
  • High risk of recurrence and metastasis.

• Anatomic location: for primary basal cell carcinoma (BCC) and SCC in healthy patients
  • High-risk areas (H-Zone) have high recurrence risk, increased need for tissue sparing, and high metastasis risk.
  • Medium-risk areas are at “reasonable risk” for tissue sparing.

• Tumor type: BCC and SCC subtypes
• Previous treatment: recurrent and incompletely excised tumors
• Patient health issues: Immunocompromised or genetic syndromes

Next, Dr Steinman moved toward referring patients for Mohs surgery. He again recommended considering referrals on the NCCN. For Mohs Surgery Appropriate Use Criteria (MAUC), he said, “MAUC are overly permissive by design. They were primarily developed to discourage Mohs surgery use in the [low-risk] area.”

Lastly, Dr Steinman discussed the rapid in-office IHC stains for melanoma and SCC. “Rapid kits are now available and Mohs surgeons are using them to treat melanoma and high-risk SCC.”

Reference
Steinman H. Understanding Mohs surgery and its indications. Presented at: Dermatology Week 2022; May 11-14, 2022; Virtual.