Combining Dermoscopy and Reflectance Confocal Microscopy to Improve External Ear Melanoma Diagnosis: A Multicenter Retrospective Study.

BACKGROUND

External ear melanoma remains poorly characterized by non-invasive imaging. We characterized dermoscopic and reflectance confocal microscopy (RCM) features of auricular melanocytic lesions and evaluated whether combining both modalities improves diagnosis.

METHODS

This multicenter retrospective study included 77 auricular lesions evaluated at three tertiary centers. Blinded readers assessed predefined dermoscopic and RCM criteria. Firth-penalized logistic regression was used to develop dermoscopy-only, RCM-only, and combined models. Model development and discrimination were internally validated with 2000 bootstrap replications.

RESULTS

Thirty melanomas, one melanocytic tumor of uncertain malignant potential, one intraepidermal atypical melanocytic proliferation of uncertain significance, and 45 nevi were analyzed. Lentigo maligna/lentigo maligna melanoma-like imaging features were observed among melanomas of several histopathological subtypes. The combined model included blue-white veil (odds ratio [OR] 10.79, 95% confidence interval [CI]: 1.72-67.72), regression structures (OR 30.16, 95% CI: 3.53-257.97), dendritic pagetoid cells (OR 5.12, 95% CI: 1.25-21.08), and medusa head-like structures (OR 10.50, 95% CI: 2.11-52.18). It outperformed the dermoscopy-only model (apparent area under the curve [AUC] 0.931 vs. 0.852, DeLong p = 0.047, Holm-adjusted p = 0.047). Selection-aware optimism-corrected AUCs were 0.899 and 0.831, respectively. Excluding the two lesions of uncertain malignant potential produced comparable results (AUC 0.952 vs. 0.863, Holm-adjusted p = 0.040).

CONCLUSIONS

Auricular melanocytic lesions warrant site-specific and sublocation-aware evaluation. Combining dermoscopy with RCM improved diagnostic discrimination over dermoscopy alone in this cohort, although prospective external validation is required.