Dermatoscopic features

https://dermnetnz.org/cme/dermoscopy-course/dermoscopic-features

🎨 Colours Seen on Dermoscopy

Black: superficial melanin (stratum corneum)
Dark brown / Tan: melanin in epidermis
Grey / Steel blue: melanin in dermis
Purple
White: fibrosis or regression
Yellow: keratin
Red: vascularity

🧭 Symmetry

Symmetrical pattern → benign
Asymmetry of colour or structure → suspicious (may indicate melanoma)
Homogeneous pattern = uniform = benign
Heterogeneous pattern = irregular = atypical or malignant

🧱 Dermatoscopic Structures of Melanocytic Lesions

Three main structures:

Pigment network
Amorphous (structureless) areas / blotches
Dots and globules

🟤 Pigment Network

Formed by melanocytes or melanin in basal keratinocytes

Dense pigment rings = rete ridges/pegs

Paler holes = dermal papillae

Seen in:

Lentigo
Junctional naevus
Compound naevus
Regular pigment network (fine and uniform; may not occupy the entire lesion)

Widened network = larger ‘holes’ in certain sites

Pseudonetwork (Facial Skin)

Annular pigmentation around hair follicles
Seen on facial skin
May mimic:
- Benign naevi
- Lentigo
- Actinic keratosis
- Lichenoid keratosis
- Early lentigo maligna

Irregular/Atypical Pigment Network

Seen in:
- Dysplastic/atypical naevi
- Melanoma
Features:
- Branched streaks (common in dysplastic naevi and melanomas)
- Radial streaming or parallel linear extensions = radial growth phase of melanoma
- Pseudopods = bulbous edge projections due to junctional nests in melanoma
- Thick lines / broadened network with irregular holes = melanoma
- Lentigo maligna = thickened lines around appendageal openings (previously “rhomboidal structures”)

_{Irregular pigment network:
red arrows point to branched streaks
black arrows to broadened network
asterisk to streaming, thin arrow to pseudopods}

Negative Pigment Network

White reticular pattern due to elongated rete pegs
Seen in:
- Melanoma (characteristic)
- Spitz naevi
- Dysplastic naevi
Differential: not to be confused with pale color between globules in benign naevi or atrophie blanche

Parallel Pattern (Palmoplantar Lesions)

Apply ink test to enhance features
Patterns:
- Parallel furrow: pigment in furrows (common in naevi)
- Lattice: furrow pattern with crossing lines
- Fibrillar/filamentous: delicate pigment across skin markings
- Parallel ridge: pigment on ridges (specific for melanoma on volar surfaces)
Homogeneous naevi: may lack visible parallel pattern

Amorphous Areas / Blotches

Lack specific structures
Causes:
- Brown blotches: pigment in basal layer or papillary dermis
- Homogeneous blue: blue naevus
Irregular blotches:
- Sometimes only feature in melanoma
- Also seen in dysplastic naevi

Dots and Globules

Represent localized pigment
Color indicates depth:
- Black dots: free melanin in stratum corneum
- Brown globules: junctional nests
- Blue/grey dots: melanophages in dermis
Benign patterns:
- Central dots/globules
- Dots on ridges (overlaying grid) or in holes (dermal papillae)
- Cobblestone pattern: uniform, angulated globules
Atypical patterns:
- Circumferential brown globules: dysplastic naevi
- Diffuse blue-grey dots without network: lichenoid keratosis
- Clusters of tiny brown dots: melanoma

⚠️ Dermatoscopic Structures of Non-Melanocytic Lesions

Useful dermoscopic clues in non-melanocytic lesions include:

Dots
Leaf-like areas
Blue ovoid masses
Milia-like cysts
Fissures and comedo-like openings
Cerebriform structures
Fingerprint-like structures

Basal Cell Carcinoma (BCC)	Seborrhoeic Keratosis	Actinic Keratosis
Dots (also in seborrhoeic keratoses) Leaf-like areas Blue ovoid masses Spoke-wheel areas (radial projections from blue ovoid) Arborising vessels (thick, branching)	Milia-like cysts Comedo-like openings (crypts) Cerebriform structure (brain-like pattern) Fingerprint structures / fat fingers Hairpin vessels with white halo	Rosettes (four white dots) Perifollicular vascular network

Dots

Seen in:
- Pigmented basal cell carcinoma (BCC) (more common)
- Seborrhoeic keratoses (rare)
Appear as small, dark pigmented foci
May resemble dots seen in melanocytic lesions but in a different context

Leaf-like Areas

Grey, brown or blue shiny, bulbous structures
Typically structureless (not associated with pigment network)
Found at edges of pigmented BCC
Often contain darker internal areas → blue ovoid masses
May also mimic moth-eaten edges of solar lentigos
Some variants may appear as general structureless areas

Blue Ovoid Masses

Large, discrete, pigmented round/oval/bullet-shaped blue structures
Characteristic of BCC
Often located within leaf-like or structureless areas
If they have radial projections → Spoke-wheel areas
Differentiate from melanoma blue blotches:
- Melanoma: less defined, irregular, out-of-focus appearance

Milia-like Cysts

Round white/yellow lesions
Represent intraepidermal keratin
Common in:
- Seborrhoeic keratoses (hallmark)
- May also occur in:
  - Dermal melanocytic naevi
  - Basal cell carcinoma
  - Melanoma (less commonly)

Fissures and Comedo-like Openings

Comedo-like openings = crypts
- Appear as dark brown craters, irregularly shaped
Fissures = clefts, often in combination with comedo-like openings
Most characteristic of:
- Seborrhoeic keratoses
May also be seen in:
- Dermal naevi
- Rarely in melanoma

Cerebriform Pattern

Seen in seborrhoeic keratosis
Brain-like appearance: pattern of fissures and ridges resembling gyri/sulci
Useful diagnostic feature, especially if milia-like cysts or comedo-like openings are absent

Fingerprint-like Structures

Tan or dark-brown, fine parallel cord-like structures
Characteristic of:
- Seborrhoeic keratoses
- Solar lentigo
Wider variants = “Fat fingers”
- Occasionally seen in melanoma

Border of Skin Lesions

Irregular edges:
- Common in melanoma
- Also seen in benign lesions → low specificity in early melanoma
Fading borders:
- Often seen in atypical/dysplastic naevi
Sharply demarcated segment:
- Suggestive of melanoma
- May occur partially or circumferentially (regular or irregular)
‘Moth-eaten’ edge:
- Appears as concave notches at the lesion periphery
- Seen in:
  - Ephelides (freckles)
  - Flat seborrhoeic keratoses
  - Lentigos (benign and lentigo maligna)

Crystalline Structures

Also known as white shiny lines, not “chrysalis structures” (outdated term)
Seen with polarised dermoscopy only
- Not visible with non-polarised contact dermoscopy
Appearance:
- Bright white, shiny streaks – can be:
  - Parallel
  - Orthogonal
  - Disordered linear
Due to collagen overproduction/fibroplasia
Commonly seen in:
- Dermatofibroma
- Scar tissue
- Basal cell carcinoma (fibroplastic subtype)
- Squamous cell carcinoma
- Spitz naevi
- Melanoma

White Shiny Areas

Similar to crystalline structures but non-linear
Includes Rosettes:
- Four white points forming a four-leaf clover shape
- Typical of actinic keratosis
- Seen only with polarised dermoscopy

🧬 Special Patterns

Negative network → melanoma, Spitz, dysplastic naevi
Pseudonetwork → facial skin (annular pigment around follicles)
Parallel ridge → melanoma (palms/soles)

🩸 Vascular Patterns (Non-Pigmented Lesions)

Condition	Vascular Pattern
Amelanotic melanoma	Dotted, corkscrew, pink blush, polymorphous vessels
Benign naevus	Comma vessels
BCC	Arborising vessels
Actinic keratosis	Perifollicular network
SCC in situ (Bowen’s disease)	Grouped glomerular vessels
Haemangioma	Red/blue/purple lacunes
Seborrhoeic keratosis	Hairpin vessels, milia-like cysts
Telangiectasia	Dilated, linear/branched vessels
Venous stasis	Small glomerular vessels
Psoriasis	Uniform globular vessels
Lichen planus	Minimal or fine linear vessels