The recognition of vascular structures under dermoscopy has become increasingly important for a range of diagnoses. The identification of specific vascular characteristics is an important element of the two-step dermoscopic algorithm. When the lesion is categorized as a nonmelanocytic lesion, vascular features can help to diagnose the lesion more specifically, and hence guide management (Level 5 of the revised two-step dermoscopic algorithm). If the lesion is clearly recognized as a melanocytic tumor, then the identification of vessel type and distribution may facilitate the differentiation between benign and malignant diagnoses (Level 6 of the revised two-step dermoscopic algorithm). For more ambiguous cases in which the lesion cannot be easily classified as melanocytic or nonmelanocytic, the clinician may need to rely on vascular structures as the only recognizable features that can assist in the diagnosis.
In conclusion, it has become apparent that a finite number of morphologically distinct blood vessels can be visualized under dermoscopy. The vessel morphology and distribution along with other accompanying features can assist the clinician in correctly identifying many benign and malignant lesions. In general, vessels in melanocytic lesions include dotted vessels, comma vessels, linear irregular vessels/serpentine vessels, milky red globules, vascular blush, and polymorphous vessels. Vessels suggestive of nonmelanocytic lesions include arborizing vessels, hairpin vessels, glomerular vessels, crown vessels, and dotted vessels in a string of pearls pattern.