Palmar and plantar melanomas differ for sex prevalence and tumor thickness but not for dermoscopic patterns

The specific anatomy of the glabrous skin, characterized by marked orthokeratosis and the presence of furrows and ridges, results in peculiar dermoscopic patterns of acral melanocytic lesions. Most frequently, acral nevi are typified by a parallel furrow pattern and acral melanoma (AM) by a parallel ridge pattern (PRP). Although the dermoscopic patterns of AM have been extensively investigated, little attention has been paid to site-related differences between palmar and plantar AM. The current study aimed to compare patients' characteristics, melanoma thickness, and the morphologic variability of AM depending on the localization on palms or soles. Patients demographics and dermoscopic images of 118 AM, including 99 (83.9%) plantar and 19 (16.1%) palmar lesions (mean thickness, 2.1 mm), were extracted from the databases of seven pigmented skin lesion clinics and were evaluated for the presence of predefined criteria. Palmar melanomas were remarkably more frequent in women (male-to-female ratio, 1/3.8) and thinner than plantar melanomas (1.3 vs. 2.2 mm). Dermoscopically, no significant differences were found between plantar and palmar melanomas, with PRP scored in 64.6 and 68.4% of plantar and palmar lesions, respectively. Non-site-specific melanoma criteria were detected in 83.9% of lesions and, among melanomas not exhibiting a PRP, 95.1% showed at least one non-site-specific melanoma criterion. In conclusion, plantar and palmar AMs show sex-related and thickness-related differences, but do not differ with respect to their dermoscopic features. For cases lacking the PRP, non-site-specific melanoma criteria may be considered as helpful additional clues for the correct diagnosis.