Introduction Clinical features under dermatoscope Polarised and non-polarised light Lesions visible Histological explanation
In dermoscopy, perpendicular white lines are short discrete white lines oriented parallel and orthogonal (perpendicular) to each other and seen only under polarised light [1]. They are also known as polarising white lines, short white lines, shiny white lines, shiny white streaks, chrysalis, chrysalids, and crystalline structures. Perpendicular white lines are a clue to a specific diagnosis including basal cell carcinoma (BCC) and some melanomas [2].
Perpendicular white lines are only seen under polarised light. They appear as short, shiny white lines and move as the dermoscopy lens is moved at different angles over the lesion.
The following pairs of images demonstrate the differences seen in dermoscopy of perpendicular white lines under polarised and nonpolarised light.
Perpendicular white lines can be seen in the following lesions:
Perpendicular white lines are thought to correlate histopathologically with altered collagen in the dermis (fibrosis). The birefringent properties of collagen bundles cause rapid randomisation of polarised light. This is the reason collagen appears bright white and is more conspicuous under polarised dermoscopy [3].
They also correlate with dermal invasion in cases of melanoma [4]. However, as our illustrations show, they may also be seen in melanoma in situ.
