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Can a Predictive Scoring Model Differentiate Subungual Melanoma in Situ From Longitudinal Melanonychia?

By: Cordi Craig
Posted: Tuesday, July 17, 2018

A recent cohort study, led by Jungyoon Ohn, MD, of Seoul National University, Republic of Korea, suggests that identifying and incorporating characteristic dermascopic features of subungual melanoma in situ (SMIS) into a predictive scoring model may help differentiate it from benign adult-onset longitudinal melanonychia. The findings may help clinicians in the examination of patients with longitudinal melanonychia affecting a single digit.

“Subungual melanoma in situ requires early diagnosis and complete surgical excision; however, little is known about the usefulness of the detailed dermascopic features of longitudinal melanonychia to predict the diagnosis of SMIS,” noted the study authors in JAMA Dermatology.

The cohort study enrolled 45 patients with pigmented nails diagnosed in a referral hospital in Seoul, South Korea. Of these patients, 19 had proven SMIS, and 26 had longitudinal melanonychia. The authors evaluated patient demographics and the frequency of specific dermascopic findings. Features such as asymmetry, border fading, multicolor pigmentation, pigmentation width of at least 3 mm, and the presence of the Hutchinson sign were significantly associated with the cancerous growth. In fact, a five-item checklist based on these morphologic features may prove to be useful for clinicians while performing nail examinations.

The authors incorporated these features into a predictive scoring model, ranging from 0 to 8 points. The model demonstrated a reliable diagnostic value in differentiating SMIS from longitudinal melanonychia at a cutoff value of 3, with a sensitivity of 89% and a specificity of 62%.

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