Rosettes and other white shiny structures in polarized dermoscopy: histological correlate and optical explanation.

BACKGROUND: Rosettes are a specific form of a white shiny structure seen with polarized dermoscopy. The precise morphological correlate and optical explication are not known.

OBJECTIVE: To estimate the frequency of rosettes in ex vivo dermoscopy and to find explication and morphologic correlate of this dermoscopic feature.

METHODS: A series of 6108 consecutive skin biopsies were examined with ex vivo dermoscopy and when rosettes were present serial transverse sections with polarization were examined.

RESULTS: In this series of 6108 consecutive skin biopsies, rosettes were found on ex vivo dermoscopy in 63 cases. When multiple we observed that they are always oriented at the same angle. Transverse sections with polarization of these lesions proved that smaller rosettes are mainly caused by polarizing horny material in adnexal openings, and larger rosettes by concentric perifollicular fibrosis.

CONCLUSIONS: Rosettes are an optical effect of crossed polarization by concentric fibrosis or horny material and hence are not lesion-specific.