Assessment of a Predictive Scoring Model for Dermoscopy of Subungual Melanoma In Situ

Abstract

Question Can dermoscopy aid in the differentiation of subungual melanoma in situ from benign longitudinal melanonychia? Findings In this cohort study of 45 patients with pigmented nails, asymmetry, border fading, multicolor pigmentation, width of the pigmentation of at least 3 mm, and presence of the Hutchinson sign were features associated with subungual melanoma in situ. A predictive scoring model incorporating these features was reliable for the detection of subungual melanoma in situ, with a sensitivity of 89% and a specificity of 62%. Meaning A predictive scoring model for the detection of subungual melanoma in situ may assist clinicians in the examination of patients with adult-onset longitudinal melanonychia affecting a single digit. Importance Subungual melanoma in situ (SMIS) is a malignant neoplasm that requires early diagnosis and complete surgical excision; however, little is known about the usefulness of the detailed dermoscopic features of longitudinal melanonychia (LM) to predict the diagnosis of SMIS. Objectives To investigate the characteristic dermoscopic findings of SMIS and to establish a predictive scoring model for the diagnosis of SMIS in patients with adult-onset LM affecting a single digit. Design, Setting, and Participants A cohort study of 19 patients with biopsy-proven SMIS and 26 patients with benign LM diagnosed in a tertiary referral hospital in Seoul, South Korea, from September 1, 2013, to July 31, 2017. Main Outcomes and Measures Patient demographics, frequency of specific dermoscopic findings, and a predictive scoring model. Results Of the total 45 patients with pigmented nails, the 19 patients with SMIS included 14 women and had a mean (SD) age of 52.0 (14.4) years, and the 26 patients with benign LM included 18 women and had a mean (SD) age of 48.1 (13.2) years. Asymmetry (odds ratio [OR], 34.00; 95% CI, 3.88-297.70), border fading (OR, 9.33; 95% CI, 2.37-36.70), multicolor (OR, 11.59; 95% CI, 2.21-60.89), width of the pigmentation of at least 3 mm (OR, 5.31; 95% CI, 1.01-28.07), and presence of the Hutchinson sign (OR, 18.18; 95% CI, 2.02-163.52) were features of LM that were significantly associated with SMIS. A predictive scoring model incorporating these dermoscopic features of SMIS was assessed. The model, ranging from 0 to 8 points, showed a reliable diagnostic value (the receiver operating characteristic curve had an area under the curve [C statistic] of 0.91) in differentiating SMIS from benign LM at a cutoff value of 3, with a sensitivity of 89% and a specificity of 62%. Conclusions and Relevance This study suggests characteristic dermoscopic features for SMIS. A predictive scoring model based on these morphologic features may help differentiate SMIS from benign LM.