Conference Coverage

Consider 9-mm surgical margins for MIS


 

REPORTING FROM SDEF HAWAII DERMATOLOGY SEMINAR

– The widely utilized 5-mm surgical margins for excision of melanoma in situ are inadequate in many cases, Christopher B. Zachary, MD, said at the Hawaii Dermatology Seminar provided by the Global Academy for Medical Education/Skin Disease Education Foundation.

Dr. Christopher B. Zachary, professor in the department of dermatology, University of California, Irvine Bruce Jancin/MDedge News

Dr. Christopher B. Zachary

“You probably should be considering more like 9- or 10-mm margins for melanoma in situ,” advised Dr. Zachary, professor and chair of the department of dermatology at the University of California, Irvine.

This has been a controversial matter. The recommendation for the long-standard 5-mm margins for excision of melanoma in situ (MIS) date back to a 1992 consensus opinion. Since then, however, persuasive data have emerged showing that 5-mm margins are often inadequate for clearance, and the latest American Academy of Dermatology guidelines for the management of primary cutaneous melanoma recommend margins of 5-10 mm (J Am Acad Dermatol. 2019 Jan;80[1]:208-50).

Dr. Zachary’s advice to go on the high side of that 5- to 10-mm zone is based in large part on studies led by John A Zitelli, MD, of the University of Pittsburgh. More than 20 years ago, Dr. Zitelli and his coinvestigators published a provocative prospective series of 535 patients whose melanomas – in situ or invasive – were excised via Mohs micrographic surgery with frozen section examination of the margins. A 9-mm margin successfully removed 95% of the melanomas, a 12-mm margin removed 97%, and a 6-mm margin successfully excised only 83% of the lesions (J Am Acad Dermatol. 1997 Sep;37(3 Pt 1):422-9).

In a follow-up study, Dr. Zitelli and his colleagues reported on a prospective series of 1,072 patients with 1,120 MIS, all excised by Mohs micrographic surgery with frozen sections (J Am Acad Dermatol. 2012 Mar;66[3]:438-44). They determined that 86% of the MIS were completely cleared using a 6-mm margin, compared with 98.9% excised with a 9 mm margin, a statistically significant difference (P less than .001).

Support for Dr. Zitelli’s stance that 5-mm margins for MIS are inadequate was provided by dermatologic surgeons at the Mayo Clinic in Scottsdale, Ariz. Of 46 patients who underwent Mohs micrographic surgery with immunostaining for excision of MIS, margins of 6 mm achieved clearance in only half of them. Surgical excision margins of 15 mm were required to successfully clear 96% of the MIS (Dermatol Surg. 2000 Aug;26[8]:771-84).

Quite a few hands shot up when Dr. Zachary asked how many members of his audience utilize 5-mm margins for surgical excision of MIS.

“That had been my practice as well until quite recently,” he said.

Dr. Zachary reported having no financial conflicts of interest regarding his presentation.

SDEF/Global Academy for Medical Education and this news organization are owned by the same parent company.

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