Perifollicular linear projections: A dermatoscopic criterion for the diagnosis of lentigo maligna on the face

Abstract

Lentigo maligna (LM) can mimic benign flat pigmented lesions and can be challenging to diagnose. To describe a new dermoscopic feature termed 'perifollicular linear projections (PLP)' as a diagnostic criterion for LM on the face. Retrospective study on reflectance confocal microscopy (RCM) and dermoscopy images of flat facial pigmented lesions originating from 2 databases. PLP were defined as short, linear, pigmented projections emanating from hair follicles. Dermoscopy readers were blinded to the final histopathologic diagnosis. From 83 consecutive LMs, 21/83 (25.3%) displayed 'bulging of hair follicles' on RCM and 18 these 21 (85.7%), displayed PLP on dermoscopy. From a database of 2,873 consecutively imaged and biopsied lesions, 252 flat pigmented facial lesions were included. PLP was seen in 47/76 melanomas (61.8%), compared with 7/176 lesions (3.9%) with other diagnosis (p<0.001). The sensitivity was 61.8% (95% CI 49.9 - 72.7%), specificity 96.0% (95% CI 92.9 - 98.4%). PLP was independently associated with LM diagnosis on multivariate analysis (OR 26.1 [95% CI 9.6 - 71.0]). Retrospective study. PLP is a newly described dermoscopic criterion that may add specificity and sensitivity to the early diagnosis of LM located on the face. We postulate that PLP constitutes an intermediary step in the LM progression model.