Clinical meaning
Dermoscopy (dermatoscopy, epiluminescence microscopy) is a non-invasive technique that uses magnification (typically 10x) and either polarized or non-polarized light to visualize subsurface skin structures not visible to the naked eye. By eliminating surface reflection and enabling visualization of the dermal-epidermal junction and superficial dermis, dermoscopy improves diagnostic accuracy for pigmented lesions by 20-30% compared to naked-eye examination.
Optical principles: Non-polarized dermoscopy requires a liquid interface (gel, oil, or alcohol) between the lens and skin to eliminate surface refraction, allowing visualization of subsurface structures. Polarized dermoscopy uses cross-polarized light that penetrates the stratum corneum without a liquid interface, visualizing deeper dermal structures. Polarized dermoscopy reveals crystalline structures, shiny white streaks, and vascular patterns better than non-polarized. Some structures are best seen with non-polarized light (milia-like cysts, comedo-like openings in seborrheic keratoses).
The two-step dermoscopic algorithm: Step 1 — Determine if the lesion is melanocytic or non-melanocytic (look for pigment network, aggregated globules, homogeneous blue pattern, or parallel pattern [acral]). Step 2 — If melanocytic, determine if it is benign, suspicious, or malignant using pattern analysis.
Melanoma-specific dermoscopic structures: atypical pigment network (irregular, broadened, broken network lines with variable mesh spacing), blue-white veil (confluent blue-white structureless area overlying irregular pigmentation — indicates melanin deep in the dermis with regression/fibrosis), irregular dots and globules (asymmetrically distributed dark structures), irregular streaks/pseudopods (linear peripheral projections indicating radial growth), regression structures (blue-gray peppering/granularity from melanophages, white scar-like areas), and atypical vascular pattern (irregular polymorphous vessels — dotted, linear irregular, milky-red areas).