Diagnostic Accuracy of Hyperpigmented Microcircles in Dermatoscopy of Non-Facial Non-Acral Melanomas: A Pilot Retrospective Study using a Public Image Database

Abstract

Background: Grey perifollicular circles are a dermatoscopic clue to melanoma, especially in facial skin. So far, no other adnexal clues than follicular have been investigated in this diagnosis. Objectives: The study aimed to analyse the prevalence of hyperpigmented periadnexal microcircles (HMs) in melanoma and its common simulators at non-facial non-acral sites, analyse the relation between the presence of HM, regression and hypopigmentation, and evaluate the diagnostic accuracy of this structure in melanoma. Methods: International Skin Imaging Collaboration (69,445 images) was searched in April 2020 for the pathology-confirmed dermatoscopic images with metadata including sex, age bin, and declared non-acral non-facial anatomic site. The final study sample (5,408 images, 1,326 of which were melanomas) was evaluated by expert dermatoscopist blinded to the diagnosis and labelled for the presence of ≥3 HM distributed centrally (cHM) or peripherally (pHM), hypopigmentation, and classic dermatoscopic regression structures. A subset of 40 images was labelled by 7 raters (2 residents, 5 experts) to assess interobserver agreement. We compared the presence of pHM with the presence of regression as well as performed a set of independent χ2 tests to evaluate the discriminatory power and its fragility. Performance of the models was assessed using measures of discrimination and calibration. Results: HM were significantly more prevalent in melanomas than in non-melanomas and nevi. Fair/good interobserver agreement for HM was reached for all the raters, and moderate/good for experts only (single rater/average, respectively). Regardless of regression/hypopigmentation status, pHM were significantly more common in melanoma than in non-melanomas or nevi and were observed significantly more often in melanomas on sun-damaged skin (upper extremity, posterior torso). No significant differences between the groups were found for cHM. pHM proved a high odds ratio in the tests as to the classical indicators such as classic dermatoscopic regression structures. Conclusion: pHM could be considered a novel dermatoscopic clue to melanoma.