Functional Surgery for Subungual Melanoma: Surgical Tips Based on Histological Analysis of 21 Cadavers

BACKGROUND Amputation has been the standard treatment for subungual melanoma. Although there is growing attention toward a more conservative functional surgery, specific operative techniques are not yet available. OBJECTIVE We aimed to provide objective measurements for use in functional surgery by analyzing the anatomy of the nail apparatus obtained from 21 cadavers. MATERIALS AND METHODS Nailbed thickness was histologically measured in each subunit, and skin surface anatomy was evaluated to determine the proximal resection margin. Immunohistochemical staining was performed to analyze microvessel distribution according to the nail subunit. RESULTS The nailbed thickness was the thinnest at the most proximal point of the nail matrix (thumbs, 1.10 +/- 0.42 mm; big toes, 1.15 +/- 0.37 mm) and the thickest at the hyponychium (thumbs, 2.86 +/- 0.82 mm; big toes, 2.72 +/- 0.84 mm). The distance from the eponychium to the skin surface closest to the bony cortex of extensor tendon insertion was 6.92 +/- 5.13 mm in thumbs and 5.14 +/- 1.59 mm in big toes. The median microvessel density was the highest at the hyponychium (25.74 vessels/mm(2)) and lowest at the germinal matrix (16.26 vessels/mm(2)) (p < .05). CONCLUSION This histological study offers practical tips, including those to help decide the proximal and deep resection margins, in functional surgery.