Quantifying the Orientation of Acquired Melanocytic Nevi on the Back

Acquired melanocytic nevi are a well-known risk factor in the development of melanoma; their increased frequency is associated with increased risk. Many recent studies have focused on the dermoscopic diagnosis of melanoma in addition to investigation of nevogenesis.^1- 2 However, the clinical appearance of nevus orientation has not been a target of investigation. Although not aiming to identify new phenomena, we attempt herein to quantify and explain the orientation patterns of acquired melanocytic nevi on the back. Blaschko lines are a well-described pattern of skin lines that correlates with epidermal nevi and may relate to acquired melanocytic nevus orientation.³ Quatresooz et al,⁴ while investigating lines of tension in skin on the back, identified a dermoscopic parallel melanotic line pattern on the normal skin of the back aligned with skin tension lines called Langer lines.⁴ We propose that a pattern of acquired melanocytic nevus orientation is identifiable and may be associated with both Blaschko and Langer lines.