Dermoscopic features

Learning objectives
Colours
Symmetry
Dermoscopic structures of melanocytic lesions
Dermoscopic structures of non-melanocytic lesions
The border of skin lesions
Vascularity
Activity

Note: dermoscopic images in this course are nearly all at the same magnification; the full width of the image is equivalent to 12 millimetres on the patient.

Learning objectives

Recognise dermoscopic features (colours and structures)

Colours

Colours

By dermoscopy, the pigmentation of the lesion is evaluated in terms of colour(s): black, dark brown, tan, grey, steel blue, purple, white, yellow and red.

Colours seen on dermoscopy
Black: epidermal melanin	Black: thrombus	Dark brown: junctional melanin	Tan: junctional melanin
Grey: upper dermal melanophages	Blue: deep dermal melanin	Purple: vascularity or bleeding	Red: vascularity or bleeding
White: regression or scarring	White: keratin	Yellow: keratin	Multiple colours (6): melanoma

Clinically, symmetry may be evaluated in terms of shape. Symmetry of shape suggests a benign lesion, and asymmetry suggests melanoma (the ‘A’ and ‘B’ of the American ABCDE's). However, an odd-shaped lesion may also be benign.

Symmetry of pattern
Homogeneous, symmetrical lesion	Symmetrical shape & structure	Symmetrical shape & structure	Homogeneous structure with asymmetrical shape

By dermoscopy, symmetry is evaluated in terms of pigment pattern (colour and/or structure). Symmetrical pigment pattern is typical of benign skin lesions. Complete asymmetry suggests the lesion may be malignant, but may also be seen in some atypical naevi.

Uniform pigment may also be called ‘homogeneous’ (benign), and an irregular pattern may be called ‘heterogenous’ (atypical or malignant).

Asymmetry of pattern
Asymmetrical shape & pattern (atypical naevus)	Asymmetrical shape & pattern (atypical naevus)	Asymmetrical shape & pattern (atypical naevus)	Symmetrical shape, asymmetrical pattern (melanoma)

Dermoscopic structures of melanocytic lesions

Melanocytic lesions are made up of three types of structure:

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

Benign lesions tend to have only one or two of these structural patterns in a symmetrical distribution. Malignant lesions tend to have areas of network, amorphous structures and scattered globules in an atypical distribution.

Pigment network

Pigment network is formed by melanocytes or melanin in basal keratinocytes. Dense pigment rings (the grid) are due to projections of rete pegs or ridges. The paler ‘holes’ are due to projections of dermal papillae.

A fine regular network is seen in some typical and atypical benign melanocytic lesions. In some sites the network is widened (larger ‘holes’). It does not have to occupy the whole lesion.

Lentigo
Junctional naevus
Compound naevus

Regular pigment network
Ink-spot lentigo	Lentigo simplex	Solar lentigo	Solar lentigo
Junctional naevus	Junctional naevus	Compound naevus	Atypical naevus
Junctional naevus Starburst pattern	Compound naevus Interrupted network	Atypical naevus Annular network	Atypical naevus Spoke-wheel network

The term ‘pseudonetwork’ is used when annular pigmentation is seen around hair follicles on facial skin. At times on the face, it may be difficult to differentiate benign naevi, lentigo, solar keratoses, lichenoid keratosis and early lentigo maligna.

Pseudonetwork: facial skin
Solar lentigo	Solar lentigo	Solar keratosis	Lichenoid keratosis

An atypical or irregular pigment network may be found in atypical or dysplastic naevi and some melanomas.

Branched streaks are seen in dysplastic naevi and some melanomas.
Radial streaming or parallel linear extensions at edge of lesion often represent the radial growth phase of melanoma.
Pseudopods are bulbous projections at the edge of the lesion due to junctional nests of abnormal melanocytes in invasive melanoma
Thick lines, also known as ‘broadened network’, are characteristic of melanoma, and are accompanied by irregular holes. Lentigo maligna is often characterised by thick lines around appendageal openings, previously referred to as ‘rhomboidal structures’.

Irregular pigment network: red arrows point to branched streaks, black arrows to broadened network, asterisk to streaming, thin arrow to pseudopods
Dysplastic naevus	Dysplastic naevus	Recurrence after excision	Atypical lentiginous hyperplasia
Melanoma	Melanoma	Melanoma	Melanoma

‘Negative pigment network’ refers to a white reticular pattern due to elongated rete pegs. It is a characteristic of melanoma but also sometimes seen in Spitz naevi and some dysplastic naevi. It may resemble the pattern seen in scars on the lower leg (atrophie blanche). It should not be confused with the pale colour separating the globules of a benign naevus.

Negative network
Melanoma	Melanoma Green arrows point to negative network	Atrophie blanche	Benign naevus

‘Parallel pattern’ refers to the network seen within most melanocytic naevi on palmar and plantar surfaces.

Parallel furrow pattern: pigmented furrows
Lattice pattern: pigmented furrows and lines crossing these
Fibrillar/filamentous pattern: delicate pigmentation crossing the skin markings
Parallel ridge pattern: pigmented ridges (white dots represent sweat duct openings). This pattern is highly specific for melanoma in volar sites.

There is no obvious parallel pattern in homogenous-type naevi on volar sites.

Dermoscopy of palmo-plantar melanocytic lesions
Parallel furrow pattern	Lattice pattern	Lattice pattern	Fibrillar pattern
Fibrillar pattern	Fibrillar pattern Dysplastic naevus	Mixed pattern	Parallel ridge pattern Melanoma

Amorphous areas

Diffuse pigmentation without specific structural features is variously described as amorphous areas or blotches.

Brown blotches may be due to pigment in the basal layer or papillary dermis and arise when the rete ridges are flattened out.
Homogeneous blue pigmentation is seen in blue naevus.

Diffuse amorphous areas
Solar lentigo	Benign naevus	Benign naevus	Blue naevus

Irregular blotches are sometimes the only dermoscopic feature of melanoma. They may also arise in dysplastic naevi.

Irregular amorphous areas
Dysplastic naevus	Melanoma	Melanoma	Melanoma Also has irregular network

Dots and globules

Globules are large dots. Dots and globules represent localised pigment. The colour determines their site: black dots are due to free melanin in the stratum corneum, brown globules are due to junctional nests of melanocytes, and blue or grey dots are due to melanophages in the dermis.

Benign lesions tend to have central black dots and globules.
Dots associated with a pigment network may be due to pigment on ridges (superimposed on the network grid) or papillae (in the holes).
Circumferential brown globules are seen in some enlarging dysplastic naevi.
Uniform globules with squarish or angulated shape are referred to as cobblestone pattern.
Diffuse blue/grey dots in the absence of a pigment network are characteristic of lichenoid keratosis.
Clusters of tiny brown dots are characteristic of melanoma.

Dots and globules in benign lesions
Central dots	Central globules	Uniform globules Dermal naevus	Cobblestone pattern Compound naevus
Scattered dots	Peripheral globules Atypical naevus	Eccentric globules Dysplastic naevus	Diffuse blue/grey dots Lichenoid keratosis

Dots and globules in melanoma: yellow arrows
Black dots	Brown dots	Grey dots	Peripheral dots

Dermoscopic structures of non-melanocytic lesions

Dots

Dots may be seen in pigmented basal cell carcinoma and rarely in seborrhoeic keratoses.

Dots in basal cell carcinoma: yellow arrows

Some specific dermoscopic structures are helpful in the diagnosis of non-melanocytic lesions. These include:

Leaf-like areas
Blue ovoid masses
Milia-like cysts
Fissures and comedo-like openings

Leaf-like areas

Leaf-like areas are grey, brown or blue shiny, discrete bulbous structures unassociated with a pigment network (structureless). They are seen on the edges of pigmented basal cell carcinoma, when they often have darker areas within them (blue ovoid masses). Some may not appear very like a leaf, in which case they are better known as ‘structureless areas’. The moth-eaten edges of solar lentigos also sometimes appear leaf-like.

Leaf-like areas
Leaf-like areas: BCC	Leaf-like areas: BCC	Structureless areas: BCC	Leaf-like areas: solar lentigo

Blue ovoid masses

Blue ovoid masses are large discrete pigmented round, oval or bullet-shaped blue structures and are characteristic of basal cell carcinoma. When the structure has radial projections, they are called ‘spoke-wheel areas’. They are often found within leaf-like or structureless areas. Blue blotches that are sometimes seen in melanoma are irregular, less well defined and appear out of focus.

Blue structures
Blue ovoid masses: BCC	Blue ovoid masses: BCC	Spoke-wheel areas: BCC	Blue blotches: melanoma

Milia-like cysts

Milia-like cysts are round white or yellow lesions due to intraepidermal keratin. They are characteristically found within a seborrhoeic keratosis. They may also arise within dermal melanocytic naevi, basal cell carcinoma (BCC) and melanoma.

Milia-like cysts
Seborrhoeic keratosis	Seborrhoeic keratosis	Compound naevus	Pigmented BCC

Fissures and comedo-like openings

Comedo-like openings are sometimes called ‘crypts’. They are little craters and tend to be dark brown, like irregular globules. They are often associated with fissures (clefts). They are characteristic of seborrhoeic keratoses, but may also be found in dermal naevi. Rarely, they may be found in melanoma.

Fissures and comedo-like openings
Comedo-like openings: seborrhoeic keratosis	Fissures: seborrhoeic keratosis	Cysts & crypts: seborrhoeic keratosis	Comedo-like openings: compound naevus

Cerebriform structure

A seborrhoeic keratosis may have a cerebriform or brain-like pattern. The pattern is composed of fissures and ridges mimicking the gyri and sulci of the brain.

This is a useful sign in the absence of comedo-like openings or milia-like cysts.


			Fissures/comedo-like openings enhanced by tanning cream

Fingerprint-like structures

These are a descriptive term for tan or dark-brown, fine parallel cord-like structures characteristically seen in seborrhoeic keratoses and solar lentigo. Wider cords are called ‘fat fingers’. Fat fingers are also rarely seen in melanoma.

Fingerprint-like structures
Fingerprint-like structures	Fingerprint-like structures Crypts in elevated centre of lesion	Fat fingers	Fat fingers

The border of skin lesions

The clinical characteristic of an irregular edge is often seen in melanoma, but is quite common in benign lesions too and is not very useful in the early diagnosis of melanoma dermoscopically.

The border of a skin lesion can fade out (often seen in atypical naevi) or be sharply demarcated in a small segment (typical of melanoma). The sharp cut-off may also occur all the way around in a regular or irregular pattern.

A ‘moth-eaten’ edge is seen as concave areas at the edge of a lesion. This edge is seen in the ephilis and some flat seborrhoeic keratoses and lentigos (benign and malignant).

Border of skin lesions
Fading border benign naevus	Localised sharp cut-off: melanoma	Sharp cut-off all round: melanoma	Moth-eaten edge: ephilis

Vascularity of skin lesions

The vascular pattern may be quite distinctive and allow diagnosis of a pink skin lesion, in the absence of pigmentation or dermoscopic structures. If using a contact dermoscope, take care not to press down on pink lesions, which will exsanguinate the vessels and make diagnosis more difficult.

Diagnosis	Vascular features
Amelanotic melanoma	Dotted or atypical or corkscrew or 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)
Solar 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 are seen, or uniform fine linear vessels

Blood vessels on dermoscopy
Pink blush Amelanotic melanoma	Polymorphous vessels Amelanotic melanoma	Comma shaped vessels Benign dermal naevus	White halo round vessels Seborrhoeic keratosis
Arborising vessels Basal cell carcinoma	Perifollicular network Solar keratosis	Focal glomerular vessels Squamous cell carcinoma in situ	Uniform lacunes Haemangioma
Dilated linear vessels Telangiectasia	Central dark lacune Thrombosed haemangioma	Uniform small globluar vessels Psoriasis	Paucity of vessels Lichen planus