Dermoscopy Introduction, Terminology and Structures (to be read in conjunction with the Diagnostic Dermoscopic Algorithm) Copyright to Cunliffe TP (Jan. 2017) All rights reserved Introduction Dermoscopy is an aid in the diagnosis of skin lesions. It must be used in conjunction with a good history and clinical examination, of which the health professional must have a good understanding. This article is set out as follows: Lesions suitable for dermoscopic examination Body site Symmetry, asymmetry, and pattern comparison Colour Dermoscopic structures Lesions suitable for dermoscopic examination Dermoscopy is very useful for most cases of seborrhoeic keratoses, angioma, dermatofibroma, lentigines, blue naevi, sebaceous gland hyperplasia and basal cell carcinoma It can be helpful in some cases of actinic keratosis, Bowen s disease and squamous cell carcinoma With increasing experience it becomes valuable in helping differentiate between benign melanocytic naevi and melanoma. However, some cases of melanoma, especially lightly-coloured lesions, and some raised lesions, may have few dermoscopic clues, as such one must always consider the following clinical signs: o o The ABCD rule for melanoma: A = Asymmetry / B = Border (irregular) / C = Colour (unusual) / D = Dimensions, changing The EFG rule for melanoma and several other skin cancers - any lesion that is all of: E = Elevated, F = Firm, G = Growth (persistent), and which cannot be recognised as benign, should be regarded as potentially malignant Body site The dermoscopic appearance of lesions at typical sites (trunk and limbs) may differ to that at special sites. The special sites are as follows: Face: especially flat facial lesions (many raised lesions, eg basal cell carcinoma, retain the same appearance as elsewhere on the body) Palms, soles and nails Mucosal surfaces Symmetry, asymmetry, and pattern comparison At a dermoscopic level symmetry refers to the arrangement of the structures within the lesion, as opposed to the shape of the lesion The greater degree of symmetry the more likely the lesion is benign Symmetry is subjective - a greater feel for what is normal comes with experience, as well as pattern comparison ie comparing one mole with another in the same patient
Colour Colour can help identify certain lesions It can also help identify at which level in the skin the lesion sits With regards to melanocytic lesions the more colours / shades of colour, the more likely a lesion is to be malignant. However, melanoma can be a single colour. It is also important to consider the natural skin, hair and eye colour of any given individual as patients of very fair colour may have moles and melanoma that produce very little colour.(ie a hypomelanotic melanoma).
Structures The terms used to describe dermoscopic structures vary. Some authors use complex terminology, more recent authors use more simplified terminology. This publication follows the latter, while still retaining some of the more useful descriptive patterns. Network - reticular ie net-like (can be angulated or rounded), or branched (NB - in this publication the term network is used as a description) Lines - straight, curved, parallel, radial (and pseudopods) Pigment bands / fissures & ridges Dots Clods Circles Ulceration and erosions Structureless Vessels
Structure 1 - Network A reticular (net-like) or branched network, may be pigmented (brown or black) or white. The reticular component can be angulated or rounded. With the exception of a dermatofibroma, a network is one of the hallmarks of a melanocytic lesion. Typical networks - pigmented or white o Benign melanocytic naevi on the trunk and limbs - the network is generally brown, and can be evenly coloured, or more pronounced in the centre, or in patients with fair skin the network is sometimes more pronounced in a symmetrical fashion around the periphery o Lentigo simplex - can be indistinguishable from the above o Benign melanocytic naevi on palms and soles - a regular brown pigment network (sometimes referred to as a lattice pattern) o Dermatofibroma - can have two networks. The most common one is subtle, usually appearing as a faint brown, rounded peripheral network. The other is a central white network o Ink-spot lentigo - has a bold reticular network, which is dark, but reassuringly monomorphic (ie appears the same throughout the lesion) o White lines can sometimes be seen in benign lesions and non-lesional skin Atypical networks o Melanoma - the network is asymmetrical, tending to have thickened brown or black component. Pattern comparison is important as a suspect lesion should appear different dermoscopically to other lesions seen in the same patient. Much less commonly the atypical network is white (sometimes referred to as a negative pigment network) o Lentigo maligna - any angulated network (grey, brown or black) on flat facial lesions is suggestive of a lentigo maligna Benign melanocytic naevus - typical pigment network Benign melanocytic naevus - typical pigment network with a darker centre
Benign melanocytic naevus in a fair-skinned individual with a typical pigment network at the periphery Dermatofibroma - a faint rounded peripheral pigment network and white structureless centre Melanoma - atypical pigment network (reticular) Melanoma - atypical pigment network (reticular and branched)
Ink-spot lentigo - this is benign. Although the pigment network is thick, the pattern Is very monomorphic ie the structures are the same throughout Melanoma - an atypical white network, which is very asymmetrical Dermatofibroma - a typical white network, which is central, and a subtle pigmented network at the periphery Benign melanocytic naevus - this is not a white network, instead it is white stroma surrounding brown clods
Lentigo maligna on the face - this is an atypical pigment network for the face as it is angulated as opposed to rounded Benign melanocytic naevus on the palms and soles - at these sites a brown pigment network (lattice pattern) is normally a good sign. Another reassuring feature are the white dots, which are the openings of the sweat glands Structure 2 - Lines A line is a linear structure where length is much greater than width. Lines take on different patterns: Straight (or curved) parallel lines can be found in: o Some solar lentigines (which also have well-demarcated borders) o The palms and soles - thin brown/black lines (sometimes referred to as a parallel furrow pattern) are seen in benign melanocytic naevi, whereas thick lines (sometimes referred to as a parallel ridge pattern) are seen in melanoma, and haemorrhage o Some melanocytic macules Other straight lines can be seen as follows: o Peripheral brown/black lines (sometimes referred to as peripheral streaks) - short brown or black lines can be seen at the periphery of both melanoma and a pigmented spindle cell naevus of Reed. In melanoma the pattern is asymmetrical, in a Reeds naevus the pattern is more symmetrical (sometimes referred to as starburst). Peripheral lines can have a bulbous end (sometimes referred to as pseudopods) o Pink, brown or black lines can be seen in nails (referred to as longitudinal melanonychia), which can be benign, malignant or drugrelated. Refer to the nail chapter at www.pcds.org.uk o Short white lines are seen most commonly as a central feature of some dermatofibroma. Less commonly they can be seen in basal cell carcinoma (BCC), and occasionally melanoma. They can also be found in benign lesions and normal skin o As part of the natural skin markings (the lines dissect across the lesion) Radial lines - these represent a collection of lines joined at a central common point and usually take the form of small solitary structures within a BCC (where they are sometimes referred to as spoke wheels)
Solar lentigo - parallel straight and curved lines Solar lentigo - parallel lines and well-demarcated border Melanoma - asymmetrical peripheral lines and pseudopods Pigmented spindle cell naevus of Reed - symmetrical peripheral lines (starbust appearance). This is a benign lesion, but histology is needed to exclude melanoma, as such patients should be referred urgently
Melanoma - white lines BCC - white lines and ulcer Natural skin markings - the white lines run though the lesion BCC - radial lines (spokewheels)
Benign melanoyctic naevus on palms and soles - thin brown parallel lines (parallel furrow pattern) and white dots (sweat gland openings) Acral melanoma - thick brown parallel lines (parallel ridge pattern). The lines are much thicker than lines seen in benign lesions at this site Longitudinal melanonychia - lines on nails can be benign, malignant or other (eg drug-related). Refer to the nail chapter at www.pcds.org.uk Subungual melanoma can be destructive
Structure 3 - Pigment bands / fissures & ridges Pigment bands are broader than lines, and can only be diagnosed in the absence of a network or other features of a melanocytic lesion. The bands, of variable length and width, are linear irregular or curved, and can be intertwined. Bands are commonly yellow or brown, but can be black. Bands are mainly seen in some thin seborrhoeic keratoses (SK), where they can develop well-defined patterns eg a coral fan appearance. As SK thicken a pattern of fissures and ridges may develop, often with a cerebriform pattern, at this stage the bands may not be apparent. Thin SK - pigment bands Thin SK - bands with a coral-like appearance SK - pigment bands SK - pigment bands developing into fissures and ridges with a cerebriform pattern as the lesion thickens SK - fissures and ridges with a cerebriform pattern
SK - fissures and ridges, white clods SK - heavily pigmented making it difficult to see individual bands. The ends of the bands are anvil-shaped (this pattern is sometimes referred to as fat fingers ). Brown-black grainy clods present Melanoma - these are NOT pigment bands, a pigment network is present Melanoma - these are NOT bands but peripheral lines/pseudopods. In addition there are black dots
Structure 4 Dots Dots (sometimes referred to as peppering) are very small, rounded structures, too small to have any other shape. White dots (sometimes referred to as milia-like cysts) are often found in SK, some benign melanocytic naevi (dermal naevi and also naevi on palms and soles), BCC, and occasionally in other malignant lesions Aggregated brown and black dots are another hallmark of melanocytic lesions. Benign lesions are more likely to have regular brown dots. Malignant lesions are more likely to have increased variation in colour and distribution Blue dots can be found together with blue clods in BCC Blue-grey dots can be found in melanoma, including in regressing melanoma Grey dots can be found in lentigo maligna (asymmetrical), lichenoid keratosis (symmetrical), and also where part of a SK has dropped off SK - white dots (milia-like cysts) Benign melanocytic naevus - brown dots Melanoma - brown and black dots and clods Melanoma - blue-grey and black dots and clods
Regressing melanoma - blue-grey dots and a white structureless area BCC - blue-grey dots and clods Lentigo maligna - asymmetrical grey dots Lichenoid keratosis - symmetrical grey dots
Structure 5 - Clods Clods - these are any well-circumscribed solid objects that are larger than a dot. Lesions can be round, oval or irregularly shaped structures that contain a solid colour. Scattered yellow-brown, brown, or occasionally black clods are seen in SK, and some benign melanocytic dermal naevi. These clods, which may have a rather grainy appearance, and are often visible to the naked-eye, are sometimes referred to as comedo-like openings Aggregated brown and black clods are another hallmark of a melanocytic lesion. More symmetrical patterns are likely to be benign. Large aggregated clods are sometimes referred to as cobblestone in appearance, which is also benign pattern. The greater the variation in size, shape, colour and distribution (including black dots and clods at periphery), the more likely the lesion is to be malignant Round or ovoid blue (or blue-grey) clods are most commonly seen in BCC. Blue-grey clods are occasionally seen in melanoma Brown irregular peripheral clods, sometimes referred to as leaf-like structures, are sometimes seen in BCC Clumped skin-coloured or yellow clods, often with a central vessel, can be found in some SK (sometimes referred to as a frogspawn appearance). Skin-coloured clods can also be found in some mature benign melanocytic naevi Grey dots and clods can sometimes be seen if a SK has dropped off Red, purple and black clods are found in angiomas, where they are sometimes referred to as lacunae White clods - scattered white clods can be seen in SK (large milia-like cysts). White clods and circles can occasionally be found in squamous cell carcinoma (SCC). Grouped white clods make up the bulk of the lesion in sebaceous gland hyperplasia SK - scattered yellow-brown grainy clods (blue arrow) and white clods (black arrow) SK - the same lesion seen clinically. Clods visible
Benign melanocytic naevus - aggregated brown clods An evolving benign melanocytic naevus - a symmetrical peripheral pattern of brown clods A benign melanocytic naevus - large aggregated clods (cobblestone) Melanoma - variation in size shape and colour of clods
Melanoma - irregular back clods BCC - round and ovoid blue clods BCC - large, irregular, peripheral brown clods (sometimes called leaflike structures) SK - clumped skin-coloured or yellow clods with central vessel
SK - grey dots and clods where part of the lesion has come away (yellow-brown clods seen in remaining lesion) Angioma - red clods (lacunae) Angioma - red-purple clods (lacunae) Angioma - black, thrombosed clods (lacunae)
Sebaceous gland hyperplasia - aggregated white clods SCC - peripheral white clods and white-yellow circles Structure 6 Circles Circles are mainly seen in flat lesions on facial skin, it is the hair follicles that give rise to this appearance: o White circles on a red background can be seen in thin actinic keratoses (sometimes referred to as strawberry-like) o o White circles on a yellow-brown background can be seen in solar lentigo Irregularly pigmented circles (often grey) can be seen in lentigo maligna White-yellow circles can sometimes be seen in SCC at any site (see above)
Actinic keratosis - white circles on a red background Solar lentigo - white circles on a yellow background Solar lentigo - white circles and yellow-brown background Lentigo maligna - more variation with some grey circles
Structure 7 - Ulceration and erosions Ulceration and erosions (a superficial ulcer) are visible both clinically and dermoscopically. Ulcers vary in size from a large ulcer (often central), to multiple small focal erosions. Visible ulceration is red, active bleeding may be seen. Sometimes the ulceration is hidden by crust, which may be one of more of yellow-orange, red, or black in colour. Ulceration can be seen in malignant lesions, as well as traumatised benign lesions. BCC - central ulcer hidden by black crust Superficial BCC - multiple erosions with yellow brown crust Hypomelanotic melanoma - bleeding ulcer, atypical vessels (circled) Traumatised SK - ulcer hidden by black crust
Structure 8 Structureless Structureless refers to an area devoid of any structure (or with very limited structures), which could be part of a lesion, or the whole lesion. The following are examples: o o o o o Dermatofibroma - a white central structureless area Bowen s disease - orange structureless areas Blue naevus - the entire lesion is usually blue-grey (sometimes white) and structureless Benign melanocytic naevi and congenital melanocytic naevi - can have skin-coloured structureless areas Melanoma An eccentric pink, brown, black, blue-white (sometimes referred to as a blue-white veil), or white structureless area can be seen as part of a melanoma. Eccentric areas are sometimes referred to as blotches Sometimes the entire lesion is structureless, eg hypomelanotic melanoma can be pink or brown-pink, especially in fair-skinned individuals. As is always the case with melanocytic lesions, pattern comparison is vital to see if the lesion in question is different to the patients other lesions ie is it an ugly duckling? Dermatofibroma - central white structureless area Bowen s disease - coiled vessels and orange structureless areas
Blue naevus - the entire lesion is blue and structureless Blue naevus - the entire lesion is blue-white and structureless A combined naevus - this is blue and brown, so not a blue naevus. The lesion was excised as melanoma could not be excluded Melanoma - a blue-white structureless area (pink arrow) and asymmetrical peripheral lines (blue arrow)
Benign melanocytic naevus - skin-coloured structureless areas Melanoma - central structureless area, irregular clods (blue arrow), peripheral lines (black arrow) Melanoma structureless, several colours Regressing melanoma - structureless white areas, blue-grey dots
All of these relatively structureless lesions are hypomelanotic nodular melanoma (original source JAMA)
Structure 9 - Vessels Identifying vascular patterns is not always easy, and contact dermatoscopes may show less vascular structures as a result of compression. The recognised vascular patters are as follows: Branching vessels (arborising) Well-focused vessels that branch in to finer secondary vessels. Mainly seen in BCC. BCC Crown vessels Barely branching peripheral vessels that do not cross the centre. Found in sebaceous gland hyperplasia (SGH) and molluscum contagiosum. SGH Comma vessels Thicker linear curved vessels with little branching, and occasionally one end thicker than the other. Mainly seen in benign melanocytic dermal naevi. Benign melanocytic dermal naevus
Looped vessels (sometimes called hairpin vessels) These are vessles that double back on themselves. They are most commonly seen in SK, and sometimes other keratinising tumours such as SCC. Sometimes, especially in SK, the vessels may sit within a halo (a). Thin elongated looped vessels can be seen, often in parallel, at the periphery of superficial BCC. Looped vessels with marked variation can sometimes be found in melanoma. a) Looped vessels in milky halo b) Standard looped vessels SK - looped vessels in milky halos Superficial BCC - thin, elongated, parallel loops at periphery
Melanoma - irregular loops Linear irregular vessels These can be found in a variety of malignant lesions such as melanoma and SCC SCC - linear irregular vessels
Melanoma - linear irregular vessels Coiled (glomerular) and helical (corkscrew) vessels Coiled vessels - tortuous capillaries coiled up in a ball. The capillaries can be so tightly packed that the vessels appear as large red dots. Seen in Bowen s disease and stasis dermatitis. Helical vessels - these are larger structures, mainly found in melanoma Coiled vessels Helical vessels Bowen s disease - coiled vessels
Melanoma - helical vessels Dotted vessels Small caliber red vessels that resemble a pinhead. Found in spitz naevi, melanoma and inflammatory conditions. Spitz naevus - dotted vessels Joined up dots give what is described as a string of pearls appearance, which is found in clear cell acanthoma.
Melanoma - dotted vessels Clear cell acanthoma - string of pearls
Polymorphous The presence of two or more vascular patterns. This pattern is suspicious for melanoma (or other life-threatening tumours) Melanoma - polymorphous pattern with dots, linear irregular vessels and a pink hue Hypomelanotic melanoma - polymorphous pattern
Generating an algorithm Please refer to the Dermoscopic Diagnostic Algorithm. Some of the key features of this are: Is the lesion melanocytic? o The defining features of a melanocytic lesion are a network (with the exception of a dermatofibroma), peripheral lines, and aggregated brown or black dots and clods If the lesion is melanocytic could it be malignant? o o o Suspect melanoma if the lesion is asymmetrical plus one or more of the following: Atypical network (pigmented or white) Peripheral lines or pseudopods Atypical dots/clods Grey or grey-blue structures Eccentric structureless areas Atypical vascular pattern (dotted, linear irregular, helical, polymorphous) Suspect melanoma at palms, soles, and nails in the presence of: Pigment bands (some of the features described above may also be present on the palms and soles) In addition for nails - a line could be the early stage of a melanoma (refer to the nail chapter at www.pcds.org.uk) / any destructive process affecting a single nail can represent a melanoma or SCC Mucosal surfaces Lips - consider melanoma in any flat pigmented lesion that is showing sustained growth, and all raised lesions Mouth and genital lesions - given that an accurate history is unlikely, all such pigmented lesions should be regarded as potentially malignant If not melanocytic, is the lesion a BCC? o Branching (arborising) vessels o Blue clods (round or ovoid) and dots o Large brown irregular peripheral clods (leaf-like structures) o Superficial BCC - focal erosions. Thin elongated looped vessels, often in parallel, at the periphery Can the lesion be recognised as a benign non-melanocytic lesion: SK, dermatofibroma, angioma, blue naevus or sebaceous gland hyperplasia? Could the lesion be an actinic keratosis, Bowen s disease or SCC? Is the lesion relatively featureless? If the lesion is dermoscopically featureless, cannot be diagnosed as any of the above, and is an ugly duckling (ie differs from the patients other lesions in terms of appearance or growth) then a melanoma or other potentially lifethreatening skin cancer should be considered as part of the differential diagnosis.