Correlation of dermoscopic structures on facial skin
Facial skin is characterized by a thin epidermis with a thin stratum corneum, a flat DEJ and multiple pilosebaceous units. These unique features imply that the pigment network is replaced by a pseudonetwork pattern instead of a pigment network.
Pseudonetwork
corresponds to structureless brown pigmentation interrupted by hypopigmented holes (Kittler et al., 2016a). Histologically, the pseudonetwork pattern corresponds to pigmented cells located in the epidermis and in a flattened DEJ interrupted by follicular openings, sebaceous or sweat glands (Marghoob and Braun, 2012; Schiffner et al., 2000).
Diagnosis of tumoral lesions occurring on the face can be challenging and generally imply a disruption of a regular pseudonetwork. Diverse dermoscopic structures have been associated with LM and LM melanoma: black blotches with obliteration of the follicles and disruption of the pseudonetwork, dark (brown or black) rhomboidal structures and zig-zag pattern (angulated lines in the interfollicular space), asymmetric follicular openings (incomplete circles), gray circles, concentric circles (circles within circles), target-like pattern (dot within a circle) and annular-granular pattern (aggregated gray dots or globules in the interfollicular area) (table 5) (Lallas et al., 2016; Schiffner et al., 2000; Tschandl et al., 2015). Histologically, these dermoscopic features correspond to a proliferation of atypical melanocytes along the DEJ and variable follicular and dermal invasion (Gómez-Martín et al., 2017; Schiffner et al., 2000)
