Research ArticlesNormal Expression of SRY-related HMG-BOX Gene 10 (SOX-10) in Recent and Old Cutaneous Scars is a Potential Mimicker of Desmoplastic Malignant MelanomaFebres-Aldana, Christopher A. MD; Alexis, John MBChBAuthor Information Arkadi M. Rywlin M.D. Department of Pathology and Laboratory Medicine, Mount Sinai Medical Center, Miami Beach, FL The authors declare no conflict of interest. Reprints: Christopher A. Febres-Aldana, MD, Arkadi M. Rywlin M.D. Department of Pathology and Laboratory Medicine, Mount Sinai Medical Center, 4300 Alton Road, Miami Beach, FL 33140 (e-mail: firstname.lastname@example.org). Received August 11, 2018 Accepted November 28, 2018 Online date: January 21, 2019 Applied Immunohistochemistry & Molecular Morphology: March 2020 - Volume 28 - Issue 3 - p 197-204 doi: 10.1097/PAI.0000000000000729 Buy Metrics Abstract Desmoplastic malignant melanoma (DMM) is an amelanotic spindle cell proliferation that can be mistaken for a cutaneous scar. The distinction can be difficult in reexcisions because DMM is negative for conventional melanoma markers such as HMB-45 and Melan-A, and scars may be positive for S-100 protein and SOX-10. We compare a total of 12 DMM cases with 8 reexcision and 35 old non–reexcision cutaneous scars using SOX-10 immunohistochemical stains. Cell quantification was performed on captured images using ImageJ 1.51t. SOX-10 was expressed in DMM (100%, 12/12), and reexcision (75%, 6/8), atrophic (88%, 22/25), hypertrophic (100%, 8/8), and keloid-type (100%, 2/2) scars. The cellular density of SOX-10 positive cells in DMM (822.9±116.9 cells/mm2, mean±SEM) was significantly higher than in any scar subgroup (hypertrophic: 188.4±20.40 cells/mm2, atrophic: 83.78±11.13 cells/mm2, reexcision: 96.72±30.13 cells/mm2, P<0.0001). Hypercellular areas in reexcision scars showed dense positivity as hypocellular areas in DMM (upper limit for scars: 258.42 positive cells/mm2 vs. lower limit for DMM: 292.42 positive cells/mm2). SOX-10 positive cells in scars are predominantly monomorphic and small following the overall directionality of the tissue. In contrast, DMM cells exhibited enlarged atypical nuclei with a haphazard distribution, invasion as single cells or in clusters, and tropism for adnexal structures (58%) and neurovascular bundles (67%). In conclusion, cutaneous scars contain SOX-10 positive cells. The evaluation of residual DMM needs careful attention to morphologic characteristics to avoid over-interpretation of SOX-10 immunostains. Copyright 2020 Wolters Kluwer Health, Inc. All rights reserved.