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

Abstract

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.