Shiny White Lines — SCE Dermatology MCQ

Correct answer: D — Spitz naevi and melanoma — they represent dermal fibrosis/collagen alteration visible under polarised light

The correct answer is D, Spitz naevi and melanoma, because orthogonal (perpendicular, cross hatched) shiny white lines are a specific pattern of shiny white streaks that correlate histologically with dermal fibrosis and altered, birefringent collagen bundles. These lines only become visible under cross polarised dermoscopy because the polarising filter removes surface glare and captures the light scatter produced by disorganised dermal collagen, an effect lost with standard non polarised contact dermoscopy. While shiny white streaks as a broader category can appear in several benign and malignant lesions, the specific orthogonal, cross hatched (chrysalis) arrangement is the pattern reported as particularly characteristic of Spitz naevi and melanoma, reflecting the marked dermal fibroplasia seen in these lesions. This feature has been incorporated into revised dermoscopic melanoma algorithms as an additional red flag structure to prompt excision or specialist referral. Why the other options are wrong: C. Dermatofibroma only: dermatofibromas classically show a central white scar like patch and peripheral pigment network, and while shiny white areas can occur, the orthogonal cross hatched pattern is not their defining or particularly associated feature, and restricting the answer to this lesion alone is incorrect. B. BCC only: nonpigmented BCC is associated with shiny white streaks and shiny white structureless areas, but the pattern more typically described in BCC is diffuse or arborising rather than the discrete orthogonal cross hatched lines, and limiting the association to BCC alone ignores the stronger melanocytic lesion link. A. Seborrhoeic keratosis: this lesion is characterised by milia like cysts, comedo like openings and a fissured, brain like surface pattern, not birefringent orthogonal white lines. E. Viral warts: dermoscopy of warts shows papillomatous, frond like surface changes with central red or brown dots (thrombosed capillaries), unrelated to dermal collagen birefringence. Key point: orthogonal, cross hatched shiny white lines seen only under polarised dermoscopy reflect dermal collagen fibrosis and are a specific red flag feature particularly associated with Spitz naevi and melanoma, warranting excision.

Reference: Dermoscopedia, Shiny white streaks and Shiny white structures, https://dermoscopedia.org/Shiny_white_streaks