Hong Kong J. Dermatol. Venereol. (2013) 21, 124-129

TTTTTokyo Wokyo Wokyo Wokyo Wokyo Women's Medical University Medical Centeromen's Medical University Medical Centeromen's Medical University Medical Centeromen's Medical University Medical Centeromen's Medical University Medical CenterEast, JapanEast, JapanEast, JapanEast, JapanEast, Japan

M Tanaka, MD, PhD

Correspondence to: Professor M Tanaka

Tokyo Women's Medical University Medical Center East,2-1-10 Nishi-Ogu, Arakawa-ku, Tokyo 116-8567, Japan

A dermoscope is a "stethoscope" for a dermatologist. It is more important to "use" dermoscopethan to "learn" it. In the first part of this review, colour and structures of the pigmented lesionson dermoscopy will be elaborated. The important features on dermoscopy to differentiatemelanoma from naevus will be discussed. The basic diagnostic approach for pigmented skinlesions will be introduced. It is essential for the readers to continue reading the second part ofthis review in the next issue in order to get the complete picture about the dermoscopy basicsand melanocytic lesions.

Keywords:Keywords:Keywords:Keywords:Keywords: Dermoscope, dermoscopy, melanocytic naevus, melanoma, pigment network

Review Article

Dermoscopy basics and melanocytic lesions (Part 1 of 2)

M Tanaka

IntroductionIntroductionIntroductionIntroductionIntroduction

Do dermatologists need dermoscopy? The answeris, of course, yes! But why? Let's think, first of all,what is special about dermatologists. We all know

that we have special eyes for a spot diagnosis ofskin disorders, which doctors in other fields maynot have. However, patients do not know thedifference of the abilities between dermatologistsand other doctors. Therefore, we need somethingspecial that distinguishes dermatologists fromothers. A dermoscope could be a special toolfor us dermatologists (Figure 1). The dermoscopeis not only an essential tool in the diagnosisof pigmented skin lesions, but also an importantbridge between a dermatologist and hispatient. A competent dermatologist using adermoscope for examination can impartadditional confidence to the patient that his skinlesion has been examined carefully.

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and blue in melanocytic lesions (Figure 3),depending of the depth of the lesions (Figure 4).Other basic colours of dermoscopy include red,yellow and white. A pigmented Spitz naevusdemonstrates black starburst pattern, naevi ofchildren mostly exhibit brown globules, whereasa dermatofibroma might show a light browndelicate pigment network and basal cellcarcinoma often reveals blue to grey leaf-likeareas. Haemangioma would show red-blacklacunas, xanthoma demonstrates yellowishhomogeneous area and a subepidermal calcifiednodule presents as white areas (Figure 3).

VVVVVariation of melanocytic naevusariation of melanocytic naevusariation of melanocytic naevusariation of melanocytic naevusariation of melanocytic naevus

A way of thinking not to miss a melanoma is toknow the variations of a naevus. If it is not anaevus, then it might be a melanoma. Otherimportant information is to understand thedermoscopic features of common differentialdiagnoses. An atypical lesion might be melanoma.

Variations of the melanocytic naevus and theclinico-pathological classification includecongenital naevus (Figure 5), naevus of Ota, bluenaevus (Figure 6), Miescher naevus (Figures 7 &8), Unna naevus (Figure 9), Clark naevus (Figure10) and Spitz naevus (Figure 11). These naevi havetheir characteristic histology, preferred sites andclinical findings (Table 1).

Basic diagnostic proceduresBasic diagnostic proceduresBasic diagnostic proceduresBasic diagnostic proceduresBasic diagnostic procedures

Diagnostic procedures for pigmented skin lesionsinclude the ABCD rule,1 Menzies method,2

7-point checklist3 and 2-step procedure adoptedby Consensus Net Meeting of Dermoscopy 2000(CNMD2000).4 The CNMD2000 evaluated thesefour methods and indicated that the 2-stepprocedure had the highest sensitivity and specificityfor the diagnosis of melanocytic lesions. Figure12 shows the basic algorithm of the 2-stepprocedure for the dermoscopic classification ofpigmented skin lesions (PSL).5 The first step is to

RRRRReading points of dermoscopyeading points of dermoscopyeading points of dermoscopyeading points of dermoscopyeading points of dermoscopy

The two important features in dermoscopy arecolours and structures. These two points areimportant because they correspond to how thelesion develops and to which depth the lesionoccurs at. For example, in melanocytic lesions, theycharacterise how melanocytes proliferate singly orin a group, or move to the periphery and whichdepth of the epidermis and dermis they proliferate.

Accordingly, the two important features ofdermoscopy that differentiate melanoma from amelanocytic naevus are an asymmetry of coloursand an asymmetry of structures, but not anasymmetry of contour (shape) (Figure 2).Everybody would admit that the lesion like Figure2A is completely symmetrical in terms of colour(brown) and structure (pigment network). However,how about the lesion like Figure 2B? Some mayfeel a little worried, but this is also completelysymmetrical in colour and structure. The reasonfor anxiety with this lesion is asymmetry of thecontour. But it should be borne in mind that, manybenign naevi are not completely symmetricalconcerning the contour and there is more or lesssome degree of irregularity. Dermoscopy helps toclarify this point and illuminates the diagnosticfeatures of colour distribution and structuralsymmetry. Figure 2D also illustrates an exampleof a benign compound naevus. This lesiondemonstrates blue homogeneous colour in thecentre and brown typical network at the periphery.The bluish colour means that there are pigmentednests of melanocytes in the upper dermis.Figure 2E also reveals a benign, junctional Clarknaevus, showing a homogeneous centre and thetypical pigment network at the periphery. However,figures 2C, 2F, 2G and 2H might indicate abeginning of early malignant melanoma, becausethey exhibit asymmetry of colours and structures.

Basic colours of dermoscopyBasic colours of dermoscopyBasic colours of dermoscopyBasic colours of dermoscopyBasic colours of dermoscopy

Observation with dermoscopy will show five basiccolours of black, dark brown, light brown, grey

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Figure 2. Figure 2. Figure 2. Figure 2. Figure 2. Dermoscopy should be based upon coloursand structure, but not contour. A, B, C and D areconsidered as completely symmetrical lesions in termsof colours and structures, but E, F, G and H are not.

Figure 1. Figure 1. Figure 1. Figure 1. Figure 1. Dermoscope is a 'stethoscope' for adermatologist. It works as a powerful tool not only fordiagnosis but also as a bridge between doctor andpatient.

Figure 3. Figure 3. Figure 3. Figure 3. Figure 3. Basic colours of dermoscopy. Eight coloursare recognised as basic dermoscopy colours. Black,dark brown, light brown, grey and blue are colourscorresponding to melanin in each depth in the skin.Red corresponds to blood, yellow to lipid and white tofibrosis, calcium deposition or thick cellular hyperplasiaor abscess, etc.

Figure 4. Figure 4. Figure 4. Figure 4. Figure 4. Melanin distribution and dermoscopic colour.The colour seen on dermoscopy depends on the depthof melanin distribution. As a general rule, melanin inthe horny layer looks black, brown in the epidermis,light brown in the basal layer, grey in the papillarydermis and blue-grey in the reticular dermis.

Figure 6. Figure 6. Figure 6. Figure 6. Figure 6. Dermoscopy of blue naevus. Global featureshows homogeneous pat tern composed ofhomogeneous blue pigmentation. There is some degreeof variation in colour from light blue to dark blue.

Figure 5. Figure 5. Figure 5. Figure 5. Figure 5. Dermoscopy of congenital naevus. Globalfeature shows reticular pattern composed of typicalpigment network at the periphery and regular dots/globules in the centre. Hypertrichosis is a feature ofcongenital naevus.

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Figure 7. Figure 7. Figure 7. Figure 7. Figure 7. Dermoscopy of Miescher naevus in children.Global feature shows reticular pattern composed oftypical pseudo-network.

Figure 9. Figure 9. Figure 9. Figure 9. Figure 9. Dermoscopy of Unna naevus. Global featureshows cobblestone pattern composed of regular dots/globules.

Figure 8. Figure 8. Figure 8. Figure 8. Figure 8. Dermoscopy of Miescher naevus in adults.Global feature shows globular pattern composed ofregular dots/globules and diffuse hypopigmentation.

Figure 11. Figure 11. Figure 11. Figure 11. Figure 11. Dermoscopy of Reed/Spitz naevus. Globalfeature shows starburst pattern composed of regularstreaks.

Figure 10. Figure 10. Figure 10. Figure 10. Figure 10. Dermoscopy of Clark naevus. Globalfeature shows reticular pattern composed of typicalpigment network.

Figure 12. Figure 12. Figure 12. Figure 12. Figure 12. Two-step procedure for the dermoscopicclassification of pigmented skin lesions. The first step isto decide whether the lesion is melanocytic or non-melanocytic. When the lesion is considered asmelanocytic, proceed to the second step and decide ifthe lesion is benign or malignant by pattern analysis.Seb K=seborrhoeic keratosis, BCC=basal cell carcinoma.

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TTTTTable 1.able 1.able 1.able 1.able 1. Classification of common naevi and characteristic features

ClassificationClassificationClassificationClassificationClassification HistologyHistologyHistologyHistologyHistology Frequent siteFrequent siteFrequent siteFrequent siteFrequent site Clinical findingClinical findingClinical findingClinical findingClinical finding

Congenital Congenital Compound Anywhere FlatOta Dermal Face Flat

Acquired Blue Dermal Face, hands NoduleMiescher Dermal, mostly Face Nodule

Unna Dermal, mostly Body VerrucousClark Junctional/compound Extremities FlatSpitz Junctional/compound Face, extremities Nodule

Figure 13. Figure 13. Figure 13. Figure 13. Figure 13. Criteria for melanocytic lesions. If one ofthese criteria is applicable, the lesion would bemelanocytic.

Figure 14. Figure 14. Figure 14. Figure 14. Figure 14. Typical pigment network of Clark naevus.The network is composed of mesh and holes.

make a decision if the lesion is melanocytic ornot and to decide if the lesion is a seborrhoeickeratosis, basal cell carcinoma or a vascular lesion.If the lesion is considered as melanocytic orunknown, then one must proceed to the secondstep and assess one whether the lesion ismalignant or benign based on the pattern analysis.

Criteria for melanocytic lesionsCriteria for melanocytic lesionsCriteria for melanocytic lesionsCriteria for melanocytic lesionsCriteria for melanocytic lesions

There are five criteria for melanocytic lesions(Figure 13): (1) pigment network, (2) aggregatedglobules, (3) branched streaks, (4) homogeneousblue pigmentation, (5) parallel pattern. If one ofthese criteria is seen on dermoscopy, the lesionwould be melanocytic; and, if not, the lesion wouldbe non-melanocytic.

The shape of pigment networkThe shape of pigment networkThe shape of pigment networkThe shape of pigment networkThe shape of pigment networkeeeeexplained by scanning electronxplained by scanning electronxplained by scanning electronxplained by scanning electronxplained by scanning electronmicroscopy (SEM)microscopy (SEM)microscopy (SEM)microscopy (SEM)microscopy (SEM)

A Clark naevus shows a reticular pattern withtypical pigment network (Figure 14). The networkconsists of mesh and holes. If the epidermis isremoved from the dermis and the dermis is viewedfrom above, dermal papillae are demonstratedon SEM (Figure 15). Each dermal papilla isconsidered to correspond to a hole of pigmentnetwork on dermoscopy. If the epidermis is

examined from the dermal side, mesh-likeepidermal rete ridges are also disclosed on SEM(Figure 16). The shape of epidermal rete ridges isequivalent to the pigment network.

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Figure 15. Figure 15. Figure 15. Figure 15. Figure 15. Scanning electron microscopy of thedermis. The dermal papillae are demonstrated aspapillary projections, which correspond to holes ofpigment network on dermoscopy (courtesy of ShuheiImayama, MD).

Figure 16. Figure 16. Figure 16. Figure 16. Figure 16. Scanning electron microscopy of theepidermis. The epidermal rete ridge is disclosed asmesh-like structure, which is equivalent to pigmentnetwork in terms of the shape (courtesy of ShuheiImayama, MD).

RRRRReferenceseferenceseferenceseferenceseferences

1. Stolz W, Riemann A, Cognetta AB, Pillet L. ABCD rule ofdermatoscopy: a new practical method for earlyrecognition of malignant melanoma. Eur J Dermatol1994:521-7.

2. Menzies SW, Ingvar C, Crotty KA, McCarthy WH.Frequency and morphologic characteristics of invasivemelanomas lacking specific surface microscopicfeatures. Arch Dermatol 1996:1178-82.

3. Argenziano G, Fabbrocini G, Carli P, De Giorgi V,Sammarco E, Delfino M. Epiluminescence microscopyfor the diagnosis of doubtful melanocytic skin lesions.Comparison of the ABCD rule of dermatoscopy and anew 7-point checklist based on pattern analysis. ArchDermatol 1998:1563-70.

4. Argenziano G, Soyer HP, Chimenti S, Talamini R, CoronaR, Sera F, et al. Dermoscopy of pigmented skin lesions:Results of a consensus meeting via the internet. J AmAcad Dermatol 2003:679-93.

5. Soyer HP, Argenziano G, Chimenti S, Menzies SW,Pehamberger H, Rabinovitz HS, et al. Dermoscopy ofpigmented skin lesions. An atlas based on the consensusnet meeting on dermoscopy 2000. Milan: Edra MedicalPublishing and New Media, 2001.