Correlation of dermoscopic structures on volar skin (palms and soles)
The palmoplantar skin is characterized by a thick cornified layer, the presence of dermatoglyphics and absence of hair follicles. In volar skin, pigment predominates in the furrows or the ridges of the dermatoplyphics. Thus, two main patterns have been described for melanocytic volar lesions: the parallel furrow pattern and the parallel ridge pattern.
Parallel furrow pattern
is characterized by thin parallel pigmented lines in the furrows and is generally associated with benign melanocytic lesions. Histologically, it corresponds to melanocytes transferring pigment to keratinocytes located on the crista limitans (furrows) (Ishihara et al., 2006).
Parallel ridge pattern
is characterized by thick parallel pigmented lines on the ridges and is associated with acral melanoma. Histologically, it reveals melanocyte proliferations around the rete ridges associated with the acrosyringia (crista intermedia) (Ishihara et al., 2006). The presence of stem cells and the microenvironment associated with the acrosyringia could explain the proliferation of malignant cells that proliferate in this location (Okamoto et al., 2014).
Other patterns that can be observed in volar skin are fibrillar pattern and lattice-like pattern.
Fibrillar pattern
(fine or fibrillar pigmentation arranged in the direction crossing the parallel skin markings) is secondary to the mechanical pressure and it is an artifactual modification of the furrow pattern (Miyazaki et al., 2005).
Lattice-like pattern
(pigmented lines across the furrows) the pigmentation is seen along the sulci of the skin markings, therefore the lattice-like pattern can be considered an anatomical modification of the parallel furrow pattern (Saida and Koga, 2007).
