Longitudinal melanonychia is a pigmented band on the nail plate that may be caused by both benign or malignant changes. There is often concern that the pigment may indicate subungual melanoma or melanoma in-situ and the diagnosis can be challenging. Consequently, a scoring system that aids clinicians in identifying high-risk lesions will be beneficial. This was a retrospective, cohort analysis of patients undergoing nail unit biopsies, with clinical images available, at a tertiary skin cancer unit. Patient images were reviewed by skin cancer specialists, and a new scoring system was applied. Scoring characteristics were: nail dystrophy, more than 40% nail involvement, Hutchinson's sign, and asymmetry. The number of nails involved (i.e. single or multiple) and the change over time were also obtained from the clinical notes. Median scores for each patient were then calculated, and a receiver operating characteristic curve was utilized to identify the score with the highest sensitivity and specificity. Seven malignant and 33 benign lesions were included. Utilizing a score of greater than or equal to 4, the London Melanonychia Assessment Tool (LMAT) had a sensitivity of 86% and a specificity of 73%. There is increasing pressure on skin cancer units, with greater numbers of urgent referrals. Although other tools for the assessment of melanonychia have been published, the LMAT includes a wide variety of lesions, making it transferable to clinical practice. The LMAT may help clinicians in identifying lesions that are higher risk and therefore should undergo biopsy or closer monitoring.
Keywords: biopsy; melanoma; nail diseases; skin cancer.
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