LAUSR

BACKGROUND Subungual melanoma (SUM) has a poor prognosis due to delayed diagnosis. The progression, consensus on surgical treatment, correlation with clinical outcomes remains unclear. OBJECTIVE We aimed to identify the pattern of dermal invasion in different locations of the nail apparatus and its relationship with prognosis. METHODS In this retrospective review of surgically treated SUM patients between January 2011 and April 2019, the nail apparatus was divided into five anatomical subunits: dorsal roof of proximal nail fold (DRPNF), ventral floor of proximal nail fold (VFPNF), germinal matrix (GM), nail bed (NB), and hyponychium. Subunit invasions were categorized using three criteria: no tumor, in situ, or invasion. RESULTS Among 44 cases of SUM, dermal invasion occurred mostly in the distal areas, with 11, 30, 18, 7, and 4 in the H, NB, GM, VFPNF, and DRPNF, respectively. The patients with hyponychial invasion showed a significantly greater Breslow depth (p=0.009), higher rate of lymph node metastasis (p=0.019), distant metastasis (p=0.036), and shorter disease-free survival (p=0.001). CONCLUSION Hyponychial invasion is an important prognostic predictor of SUM, given its strong association with invasion depth, metastatic progression, and disease-free survival. Patients with invasion in the hyponychium should undergo more strict work up, treatment, and surveillance.