Chapter 29: Mohs Micrographic Surgery

Beginner Tips

• Meticulous attention to detail is required for all steps of Mohs surgery.

• An experienced technician is vital in the preparation of high-quality slides for evaluation.

• Overlap between stages is critical to success.

• Technical errors impacting slide quality are the most common cause of recurrence after Mohs surgery.

Expert Tips

• Beware of aggressive curettage.

• Excessive facing of the block is associated with both false-positive and false-negative results.

• Patients with a history of CLL or organ transplant have a significantly higher rate of prominent inflammatory foci, increasing the challenge of slide interpretation.

Don’t Forget!

• When removing cartilage, including some noncartilaginous tissue at one edge will prevent the cartilage from floating off during processing.

• Keep in mind the risk of cerebral air emboli with exposed calvarium.

• Always overlap areas of positive tumor.

Pitfalls and Cautions

• Sectioning tissue may be associated with an increased risk of error; therefore, if appropriate, tumors may be embedded as a single unit.

• Fat should be frozen to a lower temperature to encourage appropriate cutting; this can be accomplished by using a cryogen.

Patient Education Points

• Mohs provides the highest cure rates of any technique for the treatment of skin cancer.

• Patients should come prepared for a full day at the office and bring a book, electronic device, and snacks if desired.

• For patients that are squeamish or anxious, Mohs may not represent the best option for treatment, or perioperative anxiolytics could be considered.

Billing Pearls

• Coding for Mohs is relatively straightforward, with the 17311–2 series and 17313–4 series used for tumors of the head/neck/hands/feet/genitalia and all other areas, respectively.

• The add-on codes (17312 or 17314) may never be used in isolation.

• If Mohs surgery is continued on a subsequent day, coding begins anew.

• Mohs surgery codes may never be utilized if the same physician does not act as surgeon and pathologist.

• Biopsies or frozen sections performed on the day of surgery should be billed with the appropriate modifier. Remember to document the need for the biopsy and frozen section interpretation and outline that it is distinct from the Mohs procedure.