It can improve the diagnostic accuracy of assessing pigmented lesions (early detection of melanoma).
Dermatoscopy will show typical structures in many benign skin lesions. Seborrhoeic keratosis and haemangioma, for instance, are usually easy to distinguish from pigmented lesions.
A dermatoscope is a dermatologist's routine tool. Learning to use a dermatoscope is also recommended for primary health care providers.
This article deals with the most typical indications for and basics of dermatoscopy that are important for general practitioners.
General remarks
Synonyms: dermoscopy, epiluminescence microscopy
The clinical picture, patient history and experience in using a dermatoscope are important. If the diagnosis is uncertain, a biopsy specimen should be taken (histological confirmation).
Dermatoscopy is based on microscopic examination (usually 10-fold magnification) of the skin surface.
Equipment: lighting system and loupe
Either a contact (with fluid between the dermatoscope and skin) or noncontact method can be used.
Dermatoscopy is always just an assistive tool. If there is a discrepancy between the clinical picture and the dermatoscopy finding, histological confirmation is recommended.
Dermatoscopy requires practice and experience of the correlation between the dermatoscopic picture and the histological finding (removal and histological assessment of the skin lesion).
The lesion should be removed in any case if malignancy is suspected based on the clinical picture, patient history and/or risk factors Naevi (Moles).
Structures seen on dermatoscopy
Symmetry or asymmetry (in the shape, colour or pigment structures of skin lesions)
Homogeneity/heterogeneity of the lesion
Distribution of pigment and pigment structures: brown streaks, dots, globules, unstructured areas
Superficial keratin structures: small white cysts, crypts, fissures
Appearance and distribution of blood vessels (even/uneven, atypical vessels)
Structures at the lesion margin (unclearly/clearly demarcated, radial streaks or digitate prominences)
Ulceration, blue-white veil-like structure
The biphasic algorithm of melanoma diagnosis
A biphasic algorithm can be used to diagnose melanoma. In the first phase, it should be clarified whether the lesion is melanocytic or of some other type (such as seborrhoeic keratosis, dermatofibroma, basal cell carcinoma, haemangioma).
1st phase: typical features of melanocytic lesions
Special features: parallel pattern on palms and soles, asymmetrically pigmented follicular openings on facial skin, homogeneous steel-blue colour of blue naevus
2nd phase: assessment of the malignancy of the pigmented lesion
The 3-stage checklist below has proved to be the most sensitive and simplest method.
Asymmetry (asymmetry of colour or structure in one or two axes)
Atypical network: pigment network with irregular holes and thick streaks
Blue-white structures: blue-white veil or white, cicatricial areas of regression
The aim of the checklist is to identify melanoma.
If 2 or more of the listed items are checked, melanoma is highly probable and the lesion should be removed.
Quick assessment of malignancy of a skin lesion: ”chaos and clues”
The “chaos and clues” method can be applied to any pigmented lesion. It can be used to diagnose not only melanoma but also pigmented basal and squamous cell carcinomas and pigmented Bowen's disease. The aim is not so much to obtain a precise diagnosis but to find out quickly whether a biopsy should be taken of the lesion.
Chaos refers to asymmetry of structures and colours. If there are different colours or structures on the two sides separated by a line drawn through a lesion , the lesion is asymmetric and chaotic.
If, regardless of the shape of the lesion, there is only one structure and one colour, the lesion is not chaotic.
However, exceptions to this rule include nodular lesions, small new lesions and lesions with a history of change, pigmented naevi on hands or feet with pigment on rete ridges, and any facial lesion where grey colour is detected by dermatoscopy.
Asymmetry/polymorphism of the pigment network, colour and form
Blue-white veil
Areas of regression; no pigment network
Unstructured dark area; pigment network not discernible
Abundant black dots asymmetrically distributed over the lesion or at its margins
Black dots occur in growing pigmented lesions. If the dots are evenly distributed, particularly in a naevus in a young person, it is usually a benign lesion.
If the dots are asymmetrically situated, the lesion should be removed.
Asymmetrically distributed radial streaming or pseudopods at the margins of the lesion; Images F11F5
In acral lentiginous melanoma, pigment on the sole or palm is linearly located in a parallel ridge pattern.
In facial lentigo maligna melanoma, pigment may occur in an annular-granular pattern around follicular openings or it may completely cover some follicular openings (Images F6F7).
It is quite challenging to identify amelanotic melanoma because in most cases the pigment network is completely absent. Pink, unstructured, unclear lesions should always be removed (Image F8).
In pigmented basal cell carcinoma, brown or black leaf-like structures, spoke wheel areas or pigmented elliptical areas may be seen. Additional typical features of basal cell carcinoma include arborizing blood vessels.
Nodular basal cell carcinoma often shows shiny white blotches and strands with ulceration in the centre.
Dermatoscopy of squamous cell carcinoma and preceding precancerous lesions is challenging and not completely unequivocal. Here the clinical picture is more important for the beginner.
Benign skin lesions
In this section, we first present a skin lesion visible to the naked eye and then corresponding dermatoscopic pictures.
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