Analysis of the characteristics of reflectance confocal microscopy images of xanthogranuloma and xanthoma.

Background: Both xanthogranuloma and xanthoma clinically manifest as yellowish skin lesions. Historically, the gold standard for diagnosis was skin histopathological examination. Currently, the advent of reflectance confocal microscopy (RCM) offers additional diagnostic support for these diseases by revealing their microscopic features, thereby enhancing the theoretical foundation for diagnosis.

Objective: This study aimed to elucidate the distinctive characteristics of RCM images in xanthogranuloma and xanthoma, assess their diagnostic value, and investigate the relationship between RCM and histopathological features, ultimately boosting diagnostic accuracy.

Methods: RCM and histopathological examinations were conducted on 13 patients with xanthogranuloma and 12 with xanthoma, recruited from our Dermatology Clinic between August 2022 and November 2023. The study involved analyzing RCM image features and correlating them with histopathological findings.

Results: The RCM images of 13 xanthogranuloma and 12 xanthoma cases showed similar features. Xanthogranuloma predominantly exhibited epidermal atrophy and thinning in 6 cases (46.15%). Additionally, in 69.23% of cases, scattered small mononuclear inflammatory cells were infiltrated in the superficial and middle dermis layers. Medium to high refractive cells, predominantly vacuolated and resembling foam, were observed in 61.54% of cases. All cases demonstrated high refractive cells with distinct target-shaped, disc-shaped, horseshoe-like, and flower-ring structures. Concordance rates with histopathological examinations were 69.23, 92.31, 92.31, and 100%, respectively. Regarding xanthoma, epidermal atrophy and thinning occurred in two cases (16.67%), and mononuclear inflammatory cell infiltration was observed in 25% of cases. High refractive cells with the previously mentioned shapes were present in 100% of cases, though only 16.67% displayed these characteristics exclusively. The concordance rates were 66.67, 91.67, 100, and 91.67%, respectively.

Conclusion: RCM imaging of xanthogranuloma and xanthoma presents distinctive, highly consistent features with their histopathology, offering valuable insights for clinicians in diagnosing and differentiating these conditions.