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).