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Dermoscopy and diagnosis

Dermoscopy allows GPs to triage lesions more accurately. Consultant dermatologist Dr Amanda Oakley gives 10 examples of how it can help

Dermoscopy allows GPs to triage lesions more accurately. Consultant dermatologist Dr Amanda Oakley gives 10 examples of how it can help

Dermoscopy can seem hard at first but can be very helpful in distinguishing pigmented melanocytic lesions from non-melanocytic lesions, and in determining the likelihood of a melanocytic lesion being benign or malignant.

It is not necessary to use dermoscopy to diagnose lesions that are typical clinically, although it's good practice to view as many lesions as possible. But it is most useful when evaluating lesions that are clinically atypical – often dermoscopic features can be very reassuring, reducing the necessity for follow-up or biopsy. Melanoma can be diagnosed more confidently at an early stage of its development when clinically it resembles a benign melanocytic naevus (mole) or lentigo.

Digital dermoscopic images are particularly valuable in the long-term surveillance of patients with many naevi, especially if these are atypical, or patients who are otherwise at high risk of melanoma.

It has been clearly and convincingly demonstrated that teaching GPs to use a dermatoscope allows them to triage lesions more accurately. Fewer melanomas are missed, there are fewer surgical excisions of benign lesions and fewer lesions are referred to secondary care.

The terminology of dermoscopy can seem daunting, but the ‘three-step checklist' offers a simple method of deciding whether a lesion should be referred.

The three-step checklist consists of a trio of dermoscopy criteria. These are:

• whether there is asymmetry of colour or structure of the lesion

• the presence of an atypical pigment network – thickened pigment lines or irregular distributed pigment

• whether there is any blue or grey colour within the lesion.

A score of 2 or more means that the lesion should be referred.

Below are pairs of images of the same lesion – one a normal view, one dermoscopic (inset) – with a description of the structures a dermoscope allows you to identify.

The Primary Care Dermatology Society The Primary Care Dermatology Society

The PCDS was formed in 1994 by a group of GP skin specialists who recognised the need for a forum for GPs in the UK and Ireland to exchange views on primary care dermatology, hone skills and develop clinical research.
The society also provides a voice and support forum for GPSIs in dermatology.
Our key objectives are:
• To provide an innovative forum for GPs and GPSIs with
a common interest in dermatology to exchange views and
ideas, encourage research, improve patient management and promote education both for the GP and the healthcare team.
• To encourage an interest in and provide an arena to promote and establish a clearer understanding of dermatology in primary care.
• To create wider awareness and appreciation of the benefits of shared care and to encourage strong links with specialist groups such as the British Association of Dermatologists (BAD)
The Society holds a series of educational meetings around the country from dermoscopy to surgical training to general dermatological subjects, all delivered by both GPs and consultant dermatologists.

Melanoma

A 9mm lesion with an irregular border and variable colour. Dermoscopy shows an atypical network (branched, broken-up, thickened and asymmetrical), a few scattered dots, asymmetrical blotches (featureless colours) and white scar-Melanoma Benign melanocytic naevus

A 5mm oval tan plaque. Dermoscopy shows uniform shades of brown in a globular structure, consistent with a benign melanocytic naevus arising in childhood. Benign melanocytic naevus Blue naevus

A 7mm bluish-grey macule on the buttock. Dermoscopy shows a diffuse or homogeneous steel-blue colour, characteristic of blue naevus. Blue naevus Atypical naevus

An atypical naevus, which is large (9mm) with ill-defined borders, an unusual shape and varying shades of colour. It has flat and elevated components. Dermoscopy shows a central pale globular and structureless area surrouAtypical naevus Seborrhoeic keratosis

A 9mm ‘stuck-on' brown, waxy plaque. Dermoscopy shows a roundish lesion with a sharp edge with numerous yellowish milia-like cysts and irregular keratin-filled crypts – characteristic of seborrhoeic keratosis. Seborrhoeic keratosis Basal cell carcinoma

A 7mm, roughly horseshoe-shaped shiny pinkish-brown plaque. Dermoscopy shows structureless brownish areas. There are several blue ovoid masses, flecks of brown and grey pigment, and irregular vascularity, which are fBasal cell carcinoma Dermatofibroma

A pink papule surrounded by tan pigmentation. Dermoscopy shows a white scar-like centre with radiating white lines and diffuse peripheral pigmentation, characteristic of dermatofibroma (fibrous histiocytoma). Dermatofibroma Cherry angioma

A small purple papule. Dermoscopy shows dark red lacunes (lakes) divided by whitish septa, characteristic of benign angioma. Cherry angioma Solar lentigo

A 1cm tan macule with an irregular border. Dermoscopy shows a uniform tan pseudonetwork. The pigment surrounds hair follicles, typical of solar lentigo on the face. Solar lentigo Palmar naevus

A small dark freckle on palmar skin. Dermoscopy reveals a parallel furrow pattern of pigmentation peripherally and a denser lattice pattern centrally, which is characteristic of benign melanocytic naevus on palmar skinPalmar naevus

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