Continuing medical education
How to diagnose nonpigmented skin tumors: A review of vascular structures seen with dermoscopy: Part I. Melanocytic skin tumors

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Dermoscopy is a noninvasive tool that can be helpful in the diagnosis of nonpigmented skin tumors. This is because dermoscopy permits the visualization of key vascular structures that are usually not visible to the naked eye. Much work has concentrated on the identification of specific morphologic types of vessels that allow a classification into melanocytic versus nonmelanocytic and benign versus malignant nonpigmented skin tumors. Among a broad spectrum of different types of vascular patterns, six main morphologies can be identified. These are comma-like, dotted, linear-irregular, hairpin, glomerular, and arborizing vessels. With some exceptions, comma, dotted, and linear irregular vessels are associated with melanocytic tumors, while the latter three vascular types are generally indicative of keratinocytic tumors. Aside from vascular morphology, the architectural arrangement of vessels within the tumor and the presence of additional dermoscopic clues are equally important for the diagnosis. This article provides a general overview of the dermoscopic evaluation of nonpigmented skin tumors and is divided into two parts. Part I discusses the dermoscopic vascular patterns of benign and malignant melanocytic skin tumors. Part II discusses the dermoscopic vascular patterns of benign and malignant nonmelanocytic nonpigmented skin tumors. In each part, additional special management guidelines for melanocytic and nonmelanocytic nonpigmented skin tumors, respectively, will be discussed.

Learning objectives

After completing this learning activity, participants should be able to categorize different vascular structures and the architectural arrangement of vessels within tumors and additional dermoscopic clues of nonpigmented skin tumors, recognize the diagnostic significance of vessels associated with nevi and melanoma, and appropriately manage nonpigmented melanocytic skin tumors.

Section snippets

Basic aspects to view vessels by dermoscopy

The visualization of vascular structures strongly depends on the optical device (contact or noncontact dermatoscope) and the technique of dermoscopic examination.6, 7 When using contact dermatoscopes, the contact glass plate of these instruments must be set carefully on the tumoral surface, applying minimal downward pressure. Liquids of low viscosity, such as alcohol or immersion oil, are sometimes used as contact media, but are best avoided in contact dermoscopy. This is because they require

A three-step diagnostic algorithm for the diagnosis of nonpigmented skin tumors

Key points

  1. Before beginning the dermoscopic evaluation of a given nonpigmented skin lesion, it is necessary to establish whether the lesion is a tumor or belongs to the spectrum of inflammatory or infectious skin diseases, because the vascular pattern between these two categories may overlap

  2. The dermoscopic examination of a NPST should follow a stepwise algorithm assessing the morphology of the vascular pattern, the architectural arrangement of vessels in the tumor, and the presence of additional

Comma vessels (linear curved) in dermal nevi

Key points

  1. Dermal nevi are dermoscopically characterized by a regular distribution of comma vessels, which may be of various sizes

The dermoscopic hallmark of dermal nevi are comma-like (linear curved) vessels, which show a positive predictive value (PPV) of 94%.8 These are coarse vessels that are slightly curved and barely branched (Fig 3) but can be highly variable in both size and caliber. Associated features such as terminal hairs, a few milia-like cysts or comedo-like openings, and residual brown-gray

Vascular patterns of amelanotic and hypomelanotic melanoma

The predominant vascular patterns of AHM and their arrangement strongly depend on the thickness of the tumor. The observed vascular patterns undergo time-related changes according to melanoma progression and should therefore always be correlated with the clinical palpability of a given lesion (ie, flat, elevated, or nodular). Generally, in early (flat) AHM, dotted vessels are seen, which appear homogeneous in shape and are arranged regularly. In contrast, vessels in advanced (raised) tumors are

Rare melanoma variants

Key points

  1. Nodular melanoma may lack significant vascular patterns

  2. Eczema-like melanoma should be considered in the differential diagnosis of solitary, scaly, eczematous patches or plaques that do not respond to topical treatment

  3. Dermoscopy may be helpful in the recognition of fully regressed melanoma or desmoplastic melanoma

  4. Cutaneous melanoma metastases reveal dotted or corkscrew vessels

Nodular melanoma commonly lacks any discernible vascular patterns. In such cases, polychromatism (shades of pink, white,

Four main points to avoid missing amelanotic melanoma

First, a fair proportion of AHMs are nodular.36, 37 In many instances, AHM presents as a clinically elevated tumor that is firm on palpation and may have been noted by the patient to have grown in recent weeks or months. These three characteristics are summarized in the clinical EFG rule, which can be used as a guide when dealing with melanomas lacking the classical ABCD clinical criteria.44, 45, 46, 47

Second, the true prevalence of AHM is quite low. In most cases, melanomas lacking significant

Summary

Dermal nevi exhibit specific vascular patterns that facilitate their diagnosis and assist in the differentiation from melanoma. In contrast, no reliable criteria have yet been identified that allow the differentiation of Spitzoid neoplasms from AHM. Accordingly, lesions exhibiting dotted, linear irregular, and/or polymorphous vessels should always be excised in order to avoid missing AHM.

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    Dr Zalaudek is supported by the Elise Richter Program (V9-B05) of the Austrian Science Fund (FWF).

    Conflicts of interest: The authors, editors, planners, and peer reviewers have no relevant financial relationships.

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