White shiny structures: dermoscopic features revealed under polarized light

BACKGROUND: White shiny structures, including white shiny lines, white shiny areas and rosettes, are features only observed under polarized dermoscopy (PD). OBJECTIVE: To evaluate the prevalence of the varied morphologies of white shiny structures in melanoma, basal cell carcinoma (BCC), squamous cell carcinoma (SCC), actinic keratosis (AK) and lichen planus-like keratosis (LPLK). METHODS: Retrospective study using dermoscopic images of biopsy-proven melanoma, BCC, SCC, AK and LPLK. RESULTS: A total of 538 lesions were assessed under PD. One or more types of white shiny structures were observed in 38.7% of study lesions (208/538). BCCs were significantly more likely to display a combination of white shiny areas and white shiny lines (short lines and/or ill-defined strands) (31.9%; 61/191) than any other lesions (P<0.001). BCC were more likely than other lesions to have white shiny lines distributed without any organized pattern (P<0.001). Lines in melanoma were significantly more likely than other lesion types to be oriented orthogonally (P<0.001). When white shiny lines were present, melanomas were significantly more likely than other lesions to exhibit short discrete white lines (P<0.001). Rosettes were significantly more likely to be observed in actinic tumours than other lesions (P<0.001). CONCLUSION: The presence of white shiny lines of any length accompanied by white shiny areas is most suggestive of a diagnosis of BCC (P<0.001). Melanomas are more likely to display short white shiny lines in an orthogonal distribution (P<0.001) and without white shiny areas. Actinic tumours are most likely to exhibit rosettes (P<0.001).