Ohn J, et al. - Experts assessed the characteristic dermoscopic findings of subungual melanoma in situ (SMIS) and sought to establish a predictive scoring model for the diagnosis of SMIS in patients with adult-onset longitudinal melanonychia (LM) affecting a single digit. The characteristic dermoscopic features for SMIS were suggested in the findings. SMIS could be differentiated from benign LM with the help of a predictive scoring model based on these morphologic features.

Methods

• Authors included 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 were the patient demographics, frequency of specific dermoscopic findings, and a predictive scoring model.

Results

• As per data, out of the 45 patients with pigmented nails, 19 patients had SMIS, and they included 14 women and had a mean (SD) age of 52.0 (14.4) years; the 26 patients with benign LM included 18 women and had a mean (SD) age of 48.1 (13.2) years.
• The features of LM that were significantly associated with SMIS were, 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).
• Researchers evaluated a predictive scoring model incorporating these dermoscopic features of SMIS.
• A reliable diagnostic value was demonstrated by the model, ranging from 0 to 8 points (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%.