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.