Biopsy guidelines to help your Mohs surgeon – and your patients


February 13, 2014

My daily headache as a Mohs surgeon is patients who argue that no surgery is needed because they cannot see or feel their cancer. A less frequent problem is that I can’t find the cancer site even on close scrutiny. Both of these scenarios occur, because the shave biopsy removed the entire elevated portion of the cancer.

Some suggestions to help avoid these situations are as follows: Don’t remove the entire elevated portion of lesions by shave biopsy if you’re pretty sure they are nonmelanoma skin cancer (NMSC); document lesion locations as accurately as possible; and tell patients that a biopsy is simply a sampling for diagnosis, not full lesion removal.


Dr. David Gaston

Obviously, if a patient can still see and feel a lesion after biopsy, then he or she won’t believe it was fully removed. Also, a Mohs surgeon appreciates being able to assess lesion thickness to gauge how deep to go on the first Mohs stage. Besides describing lesion size and appearance, document the lesion location using an anatomic map and/or by precise location description (e.g., left lower nasal sidewall).

Mohs surgery results can be optimized by following two other biopsy guidelines. First, don’t take punch biopsies of superficial lesions, especially on the face. Mohs sometimes removes all of the NMSC on one superficial shave excision, which could heal nicely by secondary intention, but a deeper hole in the center of the site from a punch biopsy can adversely affect cosmesis. Second, use a chemical styptic with biopsies, not electrocautery. By leaving more of a fine scar layer, which can hide the deeper portion of the carcinoma, electrocautery can lead to a false-negative Mohs result, and thus recurrence, if the Mohs surgeon performs superficial removal and doesn’t recognize the biopsy scar layer on histologic exam.

In summary, maximize patient outcome and minimize physician headache with these NMSC biopsy guidelines – take partial-lesion shave biopsies, accurately document lesion size and location, and avoid electrocautery.

Dr. David Gaston is a private-practice Mohs surgeon at the Medical Center Clinic, Pensacola, Fla., and a clinical assistant professor of dermatology at Florida State University, Tallahassee. He had no financial conflicts to disclose.