Identification of Novel Dermoscopic Patterns for "Featureless Melanoma": Clinical-Pathological Correlation

Diagnosis of melanoma can be very difficult because of its phenotypic and histological heterogeneity. Difficult-to-diagnose melanoma can be represented by mucosal melanoma, pink lesions, amelanotic melanoma (amelanotic lentigo maligna, amelanotic acral melanoma, desmoplastic melanoma), melanoma arising on sun-damaged facial skin, and "featureless melanoma". The aim of the study was to improve the identification of featureless melanoma (scoring 0-2 according to the 7-point-checklist) describing the variegated dermoscopic features and their histopathological correlation. Study samples included all melanomas excised based on clinical and/or dermoscopic findings in the period between January 2017 and April 2021. Before excisional biopsy, all lesions were recorded by means of digital dermoscopy at the department of Dermatology. Only lesions with a diagnosis of melanoma and a high quality of dermoscopic images were included in this study. After clinical and dermoscopic evaluation of 7-point checklist score, single dermoscopic and histological features were considered for lesions with a score of 2 or lower and a diagnosis of melanoma (corresponding to dermoscopic featureless melanoma). A total of 691 melanomas fulfilled inclusion criteria and were retrieved from the database. The 7-point checklist evaluation identified 19 "negative-featureless" melanoma. The 100% of the lesions with score 1 showed a globular pattern. Dermoscopy is still the best diagnostic method for melanoma. The 7-point checklist provides a simplification of standard pattern analysis because of the algorithm based on a scoring system and the lower number of features to recognize. In the daily practice it is more comfortable for many clinicians to keep in mind a list of principles that may help in the decision.