Pattern analysis

Created 2008.

Learning objectives

• Describe dermoscopic diagnosis of melanocytic lesions using pattern analysis

Introduction

In dermoscopy, the first step algorithm identifies whether a lesion is melanocytic or nonmelanocytic. Pattern analysis is the method preferred by many expert dermoscopists to diagnose melanocytic lesions and to differentiate benign melanocytic lesions from malignant melanoma. Pattern analysis refers to the simultaneous assessment of the diagnostic value of all dermoscopy features shown by the lesion.

In general terms, benign lesions have few colours, a regular structure and are symmetrical in pattern. Malignant tumours often have several colours (especially melanoma), disordered structure and asymmetry of pattern.

If conventional or morphological pattern analysis appears too complicated, use modified pattern analysis, or the 3-point checklist to identify malignant pigmented lesions.

Benign melanocytic lesions

Global pattern

• Reticular pattern (diffuse or patchy network)
• Globular pattern (globules in shades of brown)
• Homogeneous pattern (diffuse colour)
• Starburst pattern (uniform peripheral radial streaks, dots or globules)
• Parallel pattern (along furrows; palms and soles only)
• Complex pattern (2 patterns within a single lesion, usually symmetrically or regularly distributed)
• Multicomponent pattern (3 patterns, usually concentric)

Non-concentric multicomponent pattern is highly suspicious of malignancy, but is occasionally seen in benign lesions, eg collision tumours, recurrent naevus, congenital melanocytic naevus.

Reticular pattern 

Globular pattern 

Homogeneous pattern 

Starburst pattern 

Complex pattern 

Complex pattern 

Multicomponent pattern 

Multicomponent pattern 

Local features

• Pigment network, evenly spaced, fading out
• Dots/globules distributed regularly
• Streaks distributed regularly
• Central hypopigmentation
• Symmetrical blotches
• Comma-like regular vasculature
• On face: regular pseudonetwork
• On palms/soles: Parallel furrow, lattice-like or fibrillar pattern

Fading pigment network 

Regular globules 

Regular streaks 

Central hypopigmentation 

Symmetrical blotches 

Comma-like vasculature 

Symmetrical blotches/network 

Regular pseudonetwork 

Parallel furrow pattern 

Parallel lattice pattern 

Parallel fibrillar pattern 

Parallel diffuse pattern 

Melanoma

Global pattern

• Multicomponent pattern (3 or more patterns)
• Unspecific pattern (mainly structureless or 2 patterns, irregular)
• Parallel pattern (along ridges; palms and soles only)

Multicomponent pattern 

Multicomponent pattern 

Multicomponent pattern 

Parallel ridge pattern 

Local features

• Atypical pigment network (branched, broken-up, thickened, asymmetrical)
• Dots/globules distributed irregularly and of different sizes and shapes
• Asymmetrical blotches (featureless colours)
• Focal irregular streaking or peripheral linear projections (radial streaming and pseudopods)
• Five or six colours (black, brown, tan, grey, blue, red, white)
• Blue-white veil over part of the lesion
• White scar-like depigmentation
• Blue pepper-like granules
• Irregular linear or dotted vessels, or polymorphous vascular pattern especially with milky-red areas
• On face: grey dots, pseudonetwork, rhomboidal structures, asymmetrical pigmented follicles, annular-granular structures
• On palms/soles: parallel ridge, irregular

Atypical pigment network 

Irregular globules 

Asymmetrical blotches 

Focal irregular streaking 

Five to six colours 

Blue-white veil 

Scar-like depigmentation 

Blue pepper granules 

Irregular vessels 

Melanoma on the face 

Parallel ridge pattern 

Asymmetrical blotches, dots 

Modified pattern analysis

Modified or revised pattern analysis is the descriptive system described by Kittler et al, now widely adopted. Terminology is much simpler in this system than in tranditional metaphoric dermoscopic pattern recognition. It is a single step system. Describe the lesion and decide if it should be excised or not. Lesions with asymmetry of structural elements and patterns are suspicious of malignancy.

Dermoscopic features are broken down into elements: lines and rounded structures. The absence of a defined structure is described as structureless.

• Lines may be reticular, branched, parallel, radial or curved
• Rounded structures may be circles, dots, clods, pseudopods (radial line + clod) or structureless zones
• Colours are black, blue, red, light and dark brown, grey, yellow, orange, white, purple and skin coloured

Reticular brown lines 

Branched red lines 

Thick curved lines 

Parallel brown lines 

Brown and grey circles (←) 

Grey dots (←) 

Orange clods 

Pseudopods (*) 

Global dermoscopic patterns for melanocytic lesions are described using these terms.

• Reticular pattern: intersecting lines
• Radial line pattern: radial lines
• Parallel line pattern: lines in furrows or on ridges
• Clod pattern: aggregated clods
• Dotted pattern: diffuse, scattered, central or peripheral
• Structureless pattern: no lines or rounded structures
• Mixed patterns: lines + dots, lines + circles, lines + clods, structureless + lines or dots or clods

Reticular pattern 

Radial line pattern 

Parallel furrow pattern 

Mixed pattern, mainly lines 

Clod pattern 

Dotted pattern 

Structureless pattern 

Mixed pattern, mainly structureless 

Non-melanocytic lesions are made up of the same elements.

• Seborrhoeic keratosis: white / yellow clods, brown / black clods, blue / grey clods, thin or thick curved lines (fingerprinting in solar lentigo or ridges in seborrhoeic keratosis). Solar lentigo can also show reticular or structureless pattern. In addition, note sharp lesion margin. Facial lesions may have brown circles.
• Lichen-planus like keratosis is made up of grey dots.
• Pigmented basal cell carcinoma (BCC): no brown lines, brown and blue-grey dots/clods, sometimes with small or larger segmental peripheral radial lines. Pigmented and non-pigmented BCC: branched red lines, short white shiny lines, yellow/red structureless zones or clods (ulceration)
• Vascular lesions: red/blue/purple clods (angioma) or structureless zones (pyogenic granuloma). Haemorrhage is structureless, usually several colours, with a sharp border and satellite clods. Acral subcorneal haemorrhage has parallel ridge pattern.
• Dermatofibroma: structureless or intersecting fine brown or red lines in peripheral zone, often with white structureless centre, may have white shiny areas centrally. Appearance may be bland

Orange clods 

Black, white clods and circles 

Grey dots 

Thick curved lines, dark brown clods 

Brown and blue-grey dots/clods 

Blue-black clods, branched red lines 

Segmental peripheral radial lines 

Radial lines around central dot 

Branched red lines 

Red branched lines, shiny white streaks 

Shiny white streaks 

Yellow/red structureless zones 

Red clods 

Purple clods 

Blue clods 

Structureless red/brown parallel ridge pattern 

Peripheral network, central white area 

Bland, structureless pigmentation 

Prominent central white area 

Radial white shiny streaks 

Chaos and clues

Chaos means the lesion shows more than one pattern, and asymmetry of structure and/or colour on dermatoscopy. This is true for melanoma, basal cell carcinomas and squamous cell carcinomas. Consider excising the lesion if it has one or more dermoscopic clues to malignancy:

• Eccentric structureless area (any colour)
• Grey or blue structures
• Peripheral black dots or clods
• Segmental radial lines or pseudopods
• Polymorphous vessels
• White lines
• Thick lines – reticular or branched
• Parallel lines on ridges (palms and soles only)

All the melanocytic lesions illustrated in the figures below show chaos. Similar chaos and clues can be observed in the basal cell carcinomas illustrated above.

Clues to malignancy in chaotic lesions (melanoma)

Dermoscopy. Chaos and clues 

Dermoscopy. Chaos and clues 

Dermoscopy. Chaos and clues 

Dermoscopy. Chaos and clues 

Dermoscopy. Chaos and clues 

Dermoscopy. Chaos and clues 

Dermoscopy. Chaos and clues 

Dermoscopy. Chaos and clues 

Activity

Practice pattern analysis by identifying global and local features in melanocytic lesions. Do the same using modified pattern analysis terminology.