Dermoscopy has proven to be a valuable tool in the diagnosis of pigmented and nonpigmented skin lesions,^1,2 increasing the clinical diagnostic accuracy^3,4 and improving physicians' confidence in their clinical diagnosis.⁵ Until recently, dermoscopes used only nonpolarized light sources to illuminate the skin, requiring a liquid interface and direct contact between the scope and the skin. With this approach, the amount of light reflected, refracted, and diffracted at the skin surface was reduced, thereby allowing the observer to visualize structures below the stratum corneum. Nonpolarized dermoscopes have been the standard for dermoscopy training and courses and for capturing dermoscopic images for textbooks and manuscripts. However, new commercially available dermoscopes that exploit the properties of cross-polarized light have been recently introduced.^6-8 Unlike nonpolarized light dermoscopy (NPD), polarized light dermoscopy (PD) allows visualization of deep skin structures without the necessity of a liquid interface or direct skin contact with the instrument.⁹ These instruments offer the capability of viewing the skin with (polarized light contact dermoscopy [PCD]) or without (polarized light noncontact dermoscopy [PNCD]) a liquid interface and direct skin contact.

Use of dermoscopy by trained users, but not novices, improves diagnostic accuracy for cutaneous melanoma compared with naked eye examination alone.¹ Experts of dermoscopy tend to review a dermoscopic image and reach a diagnosis without use of structured analytical criteria, a diagnostic process that can be referred to as pattern analysis. Multiple simplified dermoscopic algorithms, such as the ABCD rule, the Menzies method, the 7-point checklist, the 3-point checklist, chaos and clues, and CASH (color, architecture, symmetry, and homogeneity), were developed to facilitate a novice’s ability to distinguish melanomas from nevi with high diagnostic accuracy.^2-7 A comparison of these algorithms reveals 2 diverging approaches to simplified melanoma detection (Table 1). The ABCD rule and CASH principally quantify the overall organization of a lesion by assessing features such as symmetry, architectural disorder, border sharpness, and heterogeneity in colors and structures. However, the 7-point checklist relies on the identification of atypical appearances of dermoscopic structures (eg, atypical network) in distinction from otherwise normal counterparts or on identifying unique structures strongly associated with melanoma (eg, regression). Chaos and clues, the Menzies method, and the 3-point checklist include elements of both approaches.

DURING NORMAL EMBYROGENESIS, melanoblasts migrate from the neural crest to the leptomeninges and skin. Dysregulation within this migratory pathway can result in increased proliferation of melanocytes and abnormal deposition of melanocytes and melanin in the leptomeninges—an entity known as neurocutaneous melanocytosis (NCM).^1-3 Patients with NCM may also have excess deposits of melanocytes in the skin, which can manifest clinically as the presence of multiple satellite melanocytic nevi, multiple medium-sized congenital melanocytic nevi, or large congenital melanocytic nevi (LCMN).^4,5 Patients with LCMN, a relatively rare condition affecting approximately 1 in 20 000 newborns, are at significantly high risk for developing NCM.⁶ It is reported that LCMN on the posterior axis (paraspinal, head, and neck regions) and in the presence of many satellite nevi may define a subgroup of patients at greatest risk for developing NCM.⁷