What are the melanocytic (pigmented cell) features visible on dermoscopy (skin surface microscopy)?

From the Guidelines

Melanocytic features on dermoscopy are crucial for the diagnosis of melanoma and include pigment network, aggregated globules, streaks, homogeneous blue pigmentation, and parallel patterns, which can be accurately identified by an experienced physician using dermoscopy, as evidenced by the ESMO clinical practice guidelines for diagnosis, treatment, and follow-up of cutaneous melanoma 1. When evaluating melanocytic features on dermoscopy, it is essential to consider the following characteristics:

• Pigment network: appears as interconnected brown lines forming a grid-like pattern, representing melanin in the rete ridges
• Aggregated globules: round to oval structures that correspond to nests of melanocytes
• Streaks (pseudopods and radial streaming): project from lesion borders and indicate radial growth
• Homogeneous blue pigmentation: results from melanin in the deeper dermis
• Parallel patterns: seen in acral lesions, with parallel ridge pattern suggesting melanoma and parallel furrow pattern typically indicating benign lesions Other melanocytic features that can be identified on dermoscopy include:
• Dots: small round structures smaller than globules
• Blotches: structureless areas of pigmentation
• Negative network: white lines surrounding pigmented areas These features can help differentiate benign nevi from melanoma, with asymmetry, multiple colors, and irregular structures raising suspicion for malignancy, as highlighted in the ESMO guidelines 1. The use of dermoscopy by an experienced physician enhances the diagnostic accuracy [II, B] 1, and automated videodermoscopy systems can provide improved diagnostic accuracy for patients with multiple atypical naevi in the follow-up, as well as full body imaging with high-resolution pictures, which has shown to improve early detection 1.

From the Research

Melanocytic Features on Dermoscopy

• Dermoscopy is a diagnostic method used to examine melanocytic lesions and other skin lesions, providing a bridge between the naked eye appearance of a lesion and the histopathological examination 2.
• The technique involves a two-step procedure: first, deciding if the lesion is melanocytic or not, and second, deciding if the lesion is benign or malignant if it is melanocytic 2.
• Multiple dermoscopic features have been described, including melanocytic-specific features such as peppering/granularity, shiny white streaks, typical pigment network, blotch irregular, negative network, irregular globules, dotted vessels, and blue-whitish veil 3.
• These features are useful in discriminating nevi from melanoma, with good-to-excellent agreement found for 14 of 31 features (45.2%) in a study of expert agreement on the presence and spatial localization of melanocytic features in dermoscopy 3.
• Dermoscopy has improved the detection of melanoma and other skin cancers, resulting in the detection of thinner melanomas and helping to differentiate nevi from melanomas, which has led to fewer biopsies of benign lesions 4, 5.

Diagnostic Accuracy of Dermoscopy

• The diagnostic accuracy of dermoscopy for the detection of invasive melanoma or atypical intraepidermal melanocytic variants has been evaluated in several studies, with results showing that dermoscopy is more accurate than visual inspection alone 6.
• A systematic review of 104 study publications found that dermoscopy had a higher accuracy than visual inspection alone, with a relative diagnostic odds ratio of 4.7 (95% CI 3.0 to 7.5; P < 0.001) for in-person evaluations and 5.6 (95% CI 3.7 to 8.5; P < 0.001) for image-based evaluations 6.
• The use of a named or published algorithm to assist dermoscopy interpretation did not have a significant impact on accuracy, while higher accuracy was observed for observers with high experience and for those classed as 'expert consultants' 6.

Clinical Implications

• Dermoscopy is a valuable tool to support the visual inspection of a suspicious skin lesion for the detection of melanoma and atypical intraepidermal melanocytic variants, particularly in referred populations and in the hands of experienced users 6.
• The technique may assist in triaging suspicious lesions for urgent referral when employed by suitably trained clinicians, although data to support its use in primary care are limited 6.