Positive Margins After Mohs Excision: Incidental Findings of 144 Reconstructions in the Head and Neck
Emile N. Brown, M.D.1, Christopher D. Lopez, B.A.2, Paul N. Manson, M.D.1.
1Johns Hopkins School of Medicine, Baltimore, MD, USA, 2Icahn School of Medicine at Mount Sinai, New York, NY, USA.
PURPOSE: Mohs excision of cutaneous malignancies reportedly assures complete circumferential peripheral and deep margin assessment. Therefore, when assessing a patient after Mohs resection, the reconstructive surgeon accepts there is no residual tumor. Is this assumption correct?
METHODS: Over a four-year period (2010-2013), a single surgeon (PNM) performed 144 reconstructions of head and neck Mohs defects. Referrals came from three different Mohs surgeons. At the time of reconstruction, approximately 1mm of surrounding peripheral and/or deep tissue was routinely excised in order to create a virgin wound bed. These additional margins were sent for permanent pathology.
RESULTS: Reconstructive surgery was performed after Mohs resection of 116 basal cell carcinomas, 19 squamous cell carcinomas, and 9 melanomas. The average defect size was 5.7±7.9cm2. Defects were most commonly reconstructed with local flaps (56%), followed by wide undermining and primary closure (38%). Only five defects (3%) required skin grafts. Additional permanent peripheral and/or deep margins were sent in 82% of cases. In 7 (5%) of these cases, these margins were positive for persistent malignancy. All positive margins occurred after basal cell carcinoma resection.
CONCLUSION: Pathologic analysis of additional margins after completed Mohs resection occasionally reveals persistent tumor. The clinical impact of these findings is unclear, but the reconstructive surgeon should be aware that Mohs excision does not guarantee clear margins.
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