Special locations dermoscopy: facial, acral, and nail.

Although dermoscopy reflects the anatomy, skin anatomy is different on facial and acral skin as well as in the nail unit. Malignant patterns on acral sites include the parallel ridge pattern and irregular diffuse pigmentation, whose presence should lead to a biopsy. Malignant patterns on the face include features of follicular invasion (signet-ring images, annular granular images, and rhomboidal structures) and atypical vessels. Malignant patterns on the nail unit include the micro-Hutchinson sign and irregular longitudinal lines.