A clinicopathologic analysis of 177 acral melanomas in Koreans: relevance of spreading pattern and physical stress.

IMPORTANCE The pathogenesis of acral melanoma remains unclear, even though trauma may be a predisposing factor. A study about the association of long-term physical stress with the incidence and spreading patterns through detailed anatomic mapping may be important to understand the unique features of acral melanoma. OBJECTIVES To analyze the epidemiologic and clinicopathologic characteristics of acral melanoma and evaluate how long-term physical stress or pressure strength influences acral melanoma based on the analysis of differences in incidence, prognosis of the distinct site (weight or non-weight-bearing portion of sole, volar, or subungual location), and the spreading pattern of melanoma on the soles. DESIGN, SETTING, AND PATIENTS Cross-sectional, retrospective study of 177 Korean patients with acral melanoma from January 1, 1994, through October 31, 2012. MAIN OUTCOMES AND MEASURES Anatomic mapping and histopathologic examination of acral melanoma. RESULTS The male to female ratio was 1:1.03, and the mean age at first admission was 55.3 years. Acral lentiginous melanoma was the most common histopathologic subtype (85.9%), followed by nodular melanoma (12.8%). There was a high incidence of acral melanoma at more physically stressed sites, such as the center of the heels and inner forefoot. In addition, a peculiar spreading pattern with the long axis of melanoma, typically along naturally occurring creases due to long-term pressure on the soles, was often observed. The prognostic index and survival rate showed no significant difference between volar and subungual locations or between weight and non-weight-bearing portions of the soles. CONCLUSIONS AND RELEVANCE Clinicopathologic characteristics of acral melanoma diagnosed at an advanced stage and resulting in a low survival rate are not significantly different between Koreans and other Asians. Interestingly, based on our study, long-term physical stress or pressure strength can influence the incidence and spreading pattern of acral melanoma in a particular manner. Acral melanoma occurs on more physically stressed sites with the long axis along natural creases on the sole. A further prospective investigation, especially of in situ lesions, regarding location-based differences in incidence, progress, and survival is necessary to better understand the pathophysiologic characteristics of acral melanoma.