An 18-year Review of Melanonychia and Nail Melanoma Risk in Singapore

BACKGROUND Nail apparatus melanoma (NAM) is an important variant of cutaneous melanoma in Asia and may present as longitudinal melanonychia (LM). The epidemiology of NAM in Singapore's multiethnic population is unknown. OBJECTIVE The aim of this study was to characterize demographics and melanonychia features of patients with LM, identify NAM predictors, and analyze nail unit biopsy outcomes. MATERIALS AND METHODS We conducted a retrospective observational study of patients with LM seen at the National Skin Centre, Singapore, from 2004 to 2021. Demographics, clinical features, and biopsy outcomes were analyzed descriptively. RESULTS A total of 1,556 patients were evaluated, predominantly Chinese (80.7%), female (58.0%), and younger than 50 years (63.8%). Of 274 referred patients, 198 (72.3%) underwent biopsy. Most biopsied lesions were monodactylous (79.3%), with regular borders (54.0%); Hutchinson sign was positive in 10.6%, and 33.3% showed interval increase in width. Eight NAM cases (4.0%), including 3 cases of melanoma in situ, were identified. All invasive NAM cases demonstrated nail plate destruction, nail bed ulceration, and positive Hutchinson sign. Age 50 years and older ( p = .001) and blue-collar occupation ( p = .049) were associated with malignancy. Postbiopsy complications occurred in 20.7%, most commonly nail dystrophy. CONCLUSION NAM occurred in 4.0% of biopsied LM cases. Age 50 years and older, blue-collar occupation, and monodactylous involvement warrant heightened suspicion.