Original Study: PDF OnlyDifferences Between Recommended Surgical Margins and Measured Histological Margins in Malignant Melanoma In Situ and Malignant MelanomasTababa, Erin MD; Teulings, Hansje-Eva MD, PhD; Bhawan, Jag MDAuthor Information Department of Dermatology, Dermatopathology Section, Boston University School of Medicine, Boston, MA. Correspondence: Jag Bhawan, MD, Dermatopathology Section, Department of Dermatology, Boston University School of Medicine, 609 Albany Street, J-308, Boston, MA 02118 (e-mail: [email protected]). E. Tababa, H.-E. Teulings authors contributed equally to this paper. The authors declare no conflicts of interest. IRB approval status: Reviewed and approved by the Institutional Review Board of Boston University (H-37741). The American Journal of Dermatopathology: January 26, 2021 - Volume - Issue - doi: 10.1097/DAD.0000000000001914 Buy PAP Metrics Abstract Wide local excision (WLE) using appropriate surgical margins is the standard surgical management for malignant melanoma in situ (MMIS) and primary cutaneous malignant melanoma (MM). The actual width of the histologic margins is frequently not assessed, whereas narrow histologic margins are associated with an increase in local melanoma recurrence. Our objective was to analyze the actual measured histological margins of WLE specimens of MMIS and MM cases and compare them with their recommended surgical margins. A retrospective study of formalin fixed specimens of MMIS and invasive MM treated with WLE from a large university-affiliated dermatopathology laboratory was conducted. Among a total of 164 MMIS and 128 MM cases, 14 MMIS (8.5%) and 7 MM (5.9%) had positive lateral margins. The median histologic margin for MMIS, after a 15% tissue shrinkage adjusted, was 2.7 mm [1.3–3.9] for LM type and 3.9 mm [2.3–5.6] for non-LM type, in contrast to the recommended 5-mm margin. In 96 MM of T1 type (≤1.0 mm), the median adjusted histologic margin was 6.7 mm [3.5–9.1] in contrast to the recommended 10-mm margin. These results show that measured and adjusted median histologic margins in WLE specimens in both MMIS and MM of T1 type were significantly narrower than the recommended surgical margins, regardless of anatomic location. These differences are concerning, whether they reflect clinicians' intentional or unintentional deviation from recommended guidelines. Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.