Dermoscopy of Granuloma Annulare: A Clinical and Histological Correlation Study

BACKGROUND: Dermoscopy of granuloma annulare has been investigated by several studies, but none of them took into account the variability of dermoscopic findings according to clinical characteristics and/or histological subtype. OBJECTIVE: To describe the dermoscopic features of classic granuloma annulare and seek possible dermoscopic clues related to specific clinical findings/histological subpatterns. METHODS: A representative dermoscopic image of a target lesion (the most active lesion underwent histological examination) was retrospectively assessed for the presence of specific morphological findings, correlating them with clinical variables, i.e. disease duration and extension (localized or generalized) and clinical aspect (annular or non-annular) and localization (trunk or extremities) of the biopsied lesion, and with histological subtype. RESULTS: A total of 25 lesions from 25 subjects were analysed; an "interstitial" histological variant was detected in 11 cases, while a "palisading granuloma" histological pattern was found in 14 instances. The most common dermoscopic findings included blurry vessels having variable appearance (dotted, linear-irregular, and branching) over a more or less evident pinkish-reddish background, followed by whitish and/or yellowish-orange areas. Additional findings were rosettes, crystalline structures, and whitish scaling. No difference (p > 0.05) in the frequency of dermoscopic features according to clinical findings was found, while we observed a strict association (p < 0.001) between the presence of yellowish-orange structureless areas on dermoscopy and "palisading granuloma" histology. CONCLUSION: The dermoscopic aspect of granuloma annulare is independent from clinical features but varies according to histological subtype, with the detection of yellowish-orange colour being indicative of the "palisading granuloma" variant.