About Mohs Micrographic Surgery

Mohs micrographic surgery is a procedure in which skin cancers are excised and immediately processed for review by light microscopy.  The Mohs surgeon evaluates the tissue to confirm that all of the tumor has been removed. During this time the patient is bandaged and waits for the results.  If the margins of the excised tissue is negative for tumor, then the resulting wound is repaired.  If the margins contain residual tumor cells then an additional piece of tissue is excised (termed a “stage”). This process continues until the margins are negative for tumor. The key to Mohs surgery is that it achieves complete “histological control” of the margins, due to the method in which the specimen is excised and processed. Mohs surgery achieves the lowest recurrence rate and simultaneously spares the maximum amount of healthy tissue.  This is especially important in cosmetically sensitive areas like the face.

Who should undergo Mohs surgery?

The decision as to which tumors should undergo Mohs surgery depends on the the nature of the tumor and the site. Established indications include:

  • Recurrent basal cell carcinoma (BCC) or squamous cell carcinoma (SCC);
  • BCC or SCC with clinically indistinct borders;
  • Lesions in “high-risk” areas of the face;
  • Cosmetically sensitive areas and areas with limited adjacent skin for repair, such as genitals, anal and peri-anal, hands, feet, and nail units;
  • Rapidly growing tumors;
  • Tumors >2cm in diameter;
  • Tumors with certain aggressive histological subtypes;
  • Tumors arising in sites of previous radiation treatment;
  • Tumors in immunosuppressed patients; and
  • Patients with basal cell nevus syndrome.

What will happen before, during and after Mohs surgery?

The dermatological surgeon will first review with the patient all relevant pre-operative details and medical history, including need for antibiotic prophylaxis, evaluation of clotting parameters, and the presence of implantable medical devices.

On the day of surgery, the patient is situated in the procedure room, informed consent signed, the lesion marked, and photographs taken.  The site is prepped and infiltrated with a local anesthetic, and the first “layer” excised at a 45 degree angle to the skin. The edges of the lesion and adjacent skin may be scored with a scalpel to preserve orientation. The surgical site is then temporarily bandaged while the tissue is processed and evaluated. Additional “layers” may be necessary until all of the tumor has been removed. Once the margins are “negative”, the surgeon will select an appropriate method to repair the wound, which may include primary closure, a flap or a graft. A dressing will be applied and wound care instructions provided.

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