Evaluation of MITF, SOX10, MART-1, and R21 Immunostaining for the Diagnosis of Residual Melanoma In Situ on Chronically Sun-Damaged Skin

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Abstract
BACKGROUND: Melanocytic immunostains can assist in margin evaluation of melanoma in situ (MIS) excisions; however, their accuracy and reliability relative to hematoxylin & eosin (H&E) is yet to be determined. OBJECTIVE: The objective of this study was to evaluate the sensitivity, specificity, and concordance of 4 melanocyte-specific immunostains for diagnosing MIS occurring on chronically sun-damaged skin. MATERIALS AND METHODS: Serial permanent sections from representative areas of negative margin and residual tumor were stained using H&E, MITF, MART-1, SOX10, and R21 and examined in a blinded fashion. The study set included 100 digital microscopy images from 10 cases of MIS excisions from the face. Two board-certified dermatopathologists, 4 fellowship-trained Mohs surgeons, 2 Mohs fellows, and 2 dermatology residents independently reviewed the 100 images. RESULTS: The average melanocyte density was 11 versus 28 melanocytes per 0.5 mm for chronically sun-damaged skin versus residual MIS on H&E, respectively. Statistically significantly higher melanocyte densities were observed using MITF, MART-1, and SOX10 on negative margins. The sensitivity and interobserver concordance was highest using MITF and SOX10. The intraobserver agreement on 4 duplicate images was 85%. CONCLUSION: In conclusion, the nuclear immunostains (MITF and SOX10) show the most promise for improving the diagnosis of MIS in chronically sun-damaged skin.

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