Dermoscopic Features: Essential Guide To Skin Lesion Diagnosis

Dermoscopy, also known as dermatoscopy, enhances the visualization of subsurface skin structures using 10-14x magnification and specialized lighting. This technique reveals pigmentation patterns, vascular features, and other diagnostic clues invisible to the naked eye, aiding in the differentiation of benign and malignant lesions. Images in this guide approximate 12 mm field width for consistency.

Pigmentation

By dermoscopy, lesion pigmentation is assessed by

colours

: black, dark brown, tan, grey, steel blue, purple, white, yellow, and red. These hues correspond to melanin depth and distribution, haemoglobin, or other chromophores.

• Black: Epidermal or suprabasal melanin, often in globules or structureless areas.
• Dark brown: Melanin in upper epidermis or stratum corneum.
• Tan/light brown: Diffuse epidermal melanin.
• Grey: Melanin in papillary dermis or keratin.
• Steel blue: Deep dermal melanin.
• Purple/red: Haemoglobin from blood vessels or haemorrhage.
• White: Fibrosis, hypopigmentation, or keratin.
• Yellow: Lipid droplets or serum crust.

Practice by examining personal or family moles: note predominant colours and correlate with lesion type.

Lines and Structures

Dermoscopic patterns comprise

lines

(straight, curved, wavy) and

rounded structures

(dots, globules, clods). Structureless areas lack defined patterns. These elements form global patterns like networks, streaks, or homogenous areas.

Pigment Network

**Pigment network** appears as honeycomb-like brown lines surrounding hypopigmented holes, typical of epidermal melanin in rete ridges. Variations include:

• Normal: Uniform, thin brown lines.
• Atypical: Thick, irregular, branched, or polymorphic networks signal melanoma.
• White network: Fibrotic stroma in regressing lesions or BCC.

Perifollicular networks outline hair follicles in actinic keratosis.

Dots and Globules

**Dots** are small (<0.1 mm), round, black/grey structures;

globules

are larger (0.1-0.2 mm), brown/black. Aggregates suggest naevi; irregular, confluent dots indicate melanoma.

Streaks/Radial Streaming

Irregular, finger-like projections of pigment at lesion periphery, highly suspicious for melanoma.

Structureless Zones

Homogenous hypopigmented or hyperpigmented areas without lines/structures, seen in Spitz naevi or regressing melanoma.

Vascular Features

Vessels are classified by shape, size, and distribution. Non-pigmented lesions rely heavily on vascular patterns for diagnosis.

Diagnosis	Vascular Features
Amelanotic melanoma	Dotted, atypical, corkscrew, pink blush, or polymorphous vessels
Benign melanocytic naevus	Comma-shaped vessels
Seborrhoeic keratosis	Hairpin vessels with white halo
Basal cell carcinoma	Irregular arborising vessels (thicker lesions)
Actinic keratosis	Network of perifollicular vessels
Squamous cell carcinoma in situ (Bowen disease)	Focal grouped glomerular vessels
Haemangioma	Uniform red, blue, or purple lacunes
Telangiectasia	Dilated linear and branched vessels
Haemorrhage	Red-blue lacunes within a tumour
Venous stasis	Diffuse small glomerular vessels
Psoriasis	Uniform globular vessels
Lichen planus	Very few vessels or uniform fine linear vessels

Key vascular types:

• Comma vessels: Curved, branching; benign naevi.
• Dotted vessels: Tiny red dots; melanoma or BCC.
• Glomerular vessels: Rounded loops; Bowen disease, viral warts.
• Hairpin vessels: U-shaped with white halo; seborrhoeic keratosis.
• Arborising vessels: Branching, tree-like; diagnostic for BCC.
• Lacunes: Large, round/oval spaces filled with blood; haemangioma.

Other Features

Regression

White structureless areas with grey dots/granularity (peppering) or blue-white veil indicate fibrosis and melanin/ haemorrhage remnants.

Shiny White Lines

Orthogonal or polymorphous lines from fibrosis, common in BCC and scars.

Milky Red Areas

Vascular blush in inflamed or amelanotic lesions.

Chrysalis Structures

Segmented, shiny white lines in thickened epidermis (e.g., solar lentigo).

Pattern Analysis

Expert dermoscopists use

pattern analysis

to assess global (reticular, globular, spitzoid, etc.) and local features simultaneously. Chaos (asymmetry, multiple patterns) with melanoma clues (atypical network, blue-white veil, atypical vessels) indicates malignancy.

• Global patterns: Reticular (network-dominant), globular (globule-dominant).
• Melanoma clues: Atypical pigment network, blue-white structures, atypical vascular pattern, radial streaming, dots in periphery, polymorphous vessels.

Diagnostic Algorithms

The

three-point checklist

simplifies triage: asymmetry, atypical network, blue-white structures. Presence of ≥2 suggests biopsy. Advanced algorithms like seven-point incorporate more features for higher specificity.

Clinical Application

Dermoscopy improves melanoma sensitivity/specificity when used by experts but beginners may overdiagnose. Always integrate with clinical suspicion; biopsy changing/atypical lesions. Digital imaging enables monitoring, teledermoscopy, and mole mapping.

Frequently Asked Questions (FAQs)

What magnification is standard in dermoscopy?

10-14x magnification using a high-quality dermatoscope with immersion fluid or polarized light.

Can dermoscopy diagnose all melanomas?

No, 92% show typical features; 8% require monitoring for change. Never override clinical suspicion.

What is the ugly duckling sign?

A lesion differing from a patient’s other moles, warranting closer scrutiny.

Is dermoscopy useful for non-melanoma skin cancers?

Yes, specific vascular patterns distinguish BCC (arborizing), SCC (glomerular), and others[10].

How to start learning dermoscopy?

Practice on personal lesions, use digital photography, progress through structured courses, and consult atlases.

Practice Exercises

Examine moles under dermoscopy noting colours, networks, vessels. Compare benign naevi (regular network, comma vessels) vs. suspicious (atypical features, chaos).