Twenty-five practical recommendations in primary care dermoscopy

KEYwords: Basal cell carcinoma; epiluminescence; melanoma; skin cancer; skin microscopy; squamous cell carcinoma

Dermoscopy is efficient in the early diagnosis of melanoma^1–3 and possibly efficient in diagnosing keratinocyte carcinomas.⁴ We have previously reported novel applications of dermoscopy applied in primary care.^5–7 In line with investigators in secondary care,^8,9 we reported that dermoscopy enhances the diagnosis of vascular skin lesions,¹⁰ infections¹¹ and infestations in primary care.¹²

We have pioneered dermoscope-guided surgical procedures performed in primary care.^13–15 We further reported a procedure-control study, providing evidence that dermoscope guidance lowers the risk of incomplete excision and obvious scars 6 months after the surgical procedures.¹⁶

The use of dermoscopy in primary care varies widely in different parts of the world.^17,18 We formulate here 25 recommendations from our experiences in various clinical settings. We aim to arouse the interests of primary care physicians in dermoscopy as an aid in making diagnoses and formulating plans of management.

Although melanoma makes up only 4% of all skin cancers, 80% of deaths from skin cancers are due to melanoma.¹⁹ Predisposing factors are: genetics, family history, sun exposure and Familial Atypical Multiple-Mole Melanoma Syndrome.^20,21 Melanomas rarely arise from melanocytic naevi, but early stages of melanoma can resemble dysplastic naevi.²¹ The principal aim of dermoscopy is therefore to detect and diagnose melanoma. It is not to monitor naevi to see whether they might become melanomas.¹⁸

Other aims of dermoscopy include: detecting keratinocyte carcinomas,⁴ diagnosing other skin diseases,^5–12 facilitating biopsies^13–15 and complementing dermoscope-guided surgical procedures.¹⁶

Dermoscopy in the hands of inadequately trained clinicians can be dangerous. False-positive interpretations may lead to further unnecessary and invasive procedures. False-negative interpretations might delay definitive treatment.¹⁸

Participate in courses and join online societies in dermoscopy. Most courses have a clinical component in the examination. If you pass the examination, buy a scope and start using it.

Dermoscopes with cross-polarisation have two polarising filters installed at 90° to each other. They obscure light reflected from skin surfaces, thus allowing for subsurface evaluations of lesions down to the papillary dermis. However, unpolarised dermoscopy is useful to evaluate skin surfaces for diseases such as scabies or seborrhoeic keratosis. The two views complement each other.

The left-hand dermoscope in Figure 1 delivers polarised views only. The other two scopes deliver both polarised and unpolarised modes. All of these models deliver clear images. The wireless dermoscope with a tablet in Figure 2 gives a live dermoscopic view of the lesion with image quality that is very near to the best in the present state of technology.

Figure 1. The dermoscope on the left delivers polarised non-contact dermoscopy only. The ones in the middle and the right deliver both polarised and unpolarised views with close-contact and non-contact dermoscopy. All provide clear images adequate for making clinical decisions by trained clinicians.

Figure 2. A wireless dermoscope (right) with a tablet computer. The qualities of unpolarised and polarised images are nearly unsurpassed in the present state of technology. Under expert hands, captured images may be publishable. The lesion shown is a reticular melanocytic naevus in active growth. It is symmetrical longitudinally. No clinical intervention is necessary.

Keep your hardware clean and fresh. Weak batteries, blurry lenses, opaque tissues, tissues with debris, blood and pus can obscure a good evaluation.

For medical procedures such as venepuncture, implicit consent is probably adequate as patients know what the procedure involves. However, many patients are unaware of the indications and limitations of dermoscopy. Informed oral consent usually suffices. For children and adolescents, Gillick competence^18,22 should be adequate.

We pragmatically define close non-contact dermoscopy as dermoscopy, with the distance between the probe and the lesion being ≤3 cm. This requires stability of the lesion and your scope, but usually yields clear views. The dermoscope in the left of Figure 1a is designed for non-contact dermoscopy. All the scopes in Figures 1 and 2 allow for both.

For contact dermoscopy, we need protection not only from bacteria and fungi, but also from viruses such as extragenital variants of human papillomaviruses.²³ Simple sanitation measures such as applying alcohol swabs are therefore inadequate. We recommend placing a disposable glass slide between the probe and the skin.²⁴ Take extra care to prevent the sides of the slide from injuring the skin. Otherwise the vasculature will be attenuated.

Multiple algorithms have been established and validated for the dermoscopic evaluation of skin cancers. Become familiar with them, but choose one that works for you. We advocate the Chaos and Clues Algorithm established and validated by Clues Algorithm^25–27 because this approach is simple, easy to learn and evidence-based. It is applicable to all pigmented skin lesions. The results will indicate whether a biopsy is required.

However, this algorithm does not provide an exact diagnosis. If you can ascertain if the lesion is a seborrhoeic keratosis, you can override the algorithm.^25–27 For adults, if a lesion is changing, nodular or with grey circles seen on the head and neck, we would excise and not apply the algorithm. If the pigmentation is patterned as parallel lines on the ridges of acral regions (palms and soles), we also recommend excision.

Your clinical experience and common sense are invaluable. If your clinical diagnosis is incompatible with the outcome suggested by the algorithm, apply other algorithms. For indeterminate lesions, it is best to biopsy.

Apart from the trunk and limbs, there are special rules for interpreting dermoscopic images from the scalp, face, acral regions, nails, genitalia and mucosal surfaces. Understand these rules. You may later find that interpreting dermoscopic images from these special regions is actually easier than interpreting trunk and limb lesions.

Backup your clinical and dermoscopic images regularly, if not concomitantly. Your computer should allow you to retrieve images according to the dates and times the images were taken. You can then locate the clinical photos by the dates and times from your clinical records; the additional image files are your dermoscopic images for the same patient.

Always retain the original uncompressed images. This is important clinically and for medical–legal reasons. This is analogous to ‘strikethrough’, striking through wrongly written words in the clinical records, with the original words still being readable.

Apply the highest magnification possible. Figure 3a is a camera shooting the back of another camera. A polarised dermoscopic image capturing a melanocytic lesion on the sole is seen. Figure 3b shows this image being magnified. The image is clearer, and interpretation is easier.

Figure 3. (a) An image of one camera shooting the back panel of another camera. A polarised dermoscopic image capturing a melanocytic lesion on acral skin (the soles here) is seen. Analysing and demonstrating such to the patient could be challenging. (b) In-camera digital magnification of the image in (a). The image is much more easily interpreted and explained to the patient than using (a). The narrower vertical strips represent the furrows (A). The wider vertical strips are the ridges (B). The eccrine sweat pores are seen on the ridges (C). The parallel hyperpigmentations are seen in the furrows (D). The lesion is symmetric in pattern and colours, and is compatible with a melanocytic naevus. Melanoma should be considered if the parallel hyperpigmentations are seen on the ridges.

Apply other in-camera improvisations such as adjustments of contrast, hue and colour saturations. In experienced hands, augmented images can be much more easily interpreted.

Whenever feasible, show augmented dermoscopic images to patients and their families. This will help them develop deeper understanding regarding the diseases and the treatment options.¹⁸

One example was a girl with a clinical diagnosis of trichotillomania. Despite detailed discussions, her mother found it difficult to accept the diagnosis. We captured polarised dermoscopic images, such as Figure 4a, where the features of trichotillomania are not obvious. When shown augmented images such as Figure 4b, with broken and kinking hairs at variable stages of hair growth, and an inflammatory background, but with no exclamation mark, the mother accepted our diagnosis. We then referred the girl for psychiatric assessments and kept providing primary care longitudinally for the family.

Figure 4. (a) Dermoscopic image on the scalp of a girl with trichotillomania diagnosed clinically. The mother found it difficult to accept our diagnosis. (b) An augmented and annotated view of (a). Comparison with other dermoscopic images confirmed the asymmetry of hair loss. Kinking and broken hairs at variable stages of hair growth are obvious (circled in red). An inflammatory background is present. No exclamation mark is seen. The mother thus accepted our diagnosis. These represent virtually pathognomonic dermoscopic evidence of trichotillomania (apart from trichotillomania-by-proxy as one of the manifestations of Munchausen Syndrome-by-proxy).

Toggling means viewing dermoscopic images taken in the same position and magnification with and without cross-polarisation alternatively and repeatedly at one or two frames per second (Figure 5a, b).¹⁸ Some clinicians find that this manoeuvre enhances their conceptualisation of the three-dimensional architecture of lesions, thus facilitating diagnosis and plans for surgical procedures.

Figure 5. (a) Dermoscopic image with no cross-polarisation for a globular melanocytic naevus. (b) Dermoscopic image with cross-polarisation for the naevus at the same position and magnification as (a). Viewing (a) and (b) alternating at around one frame per second (toggling) would leave the clinician an enhanced impression for the three-dimensional architecture and parameters of the lesion.

Skin lesions in hair-bearing and concave areas such as interdigital sites and skin creases may not allow for proper focusing. In such sites, apply dermoscopes with small probes, such as the one in Figure 2. Figures 6a and 6b demonstrate the results.

Figure 6. (a) A pigmented lesion just inferior to the right mandibular angle. Focusing via our usual dermoscope failed, owing to the lesion being in a concave region of the body. (b) Application of another dermoscope with a smaller probe led to this polarised image of sufficient quality for making a diagnosis of globular melanocytic naevus with full symmetry for patterns and colours.

For lesions in skin creases, far (>3 cm), non-contact dermoscopy is another option, although minute movements of the patient or dermoscope will jeopardise the focus. Patients might therefore need to be lying down on an examination couch. The dermoscope would be secured by stands and clamps vertically and directly above the lesion, with the probe heading down. Far, non-contact dermoscopy is mandatory for performing dermoscope-guided surgical procedures.^13–16

Stretching and contracting the skin may offer improved images for cysts, mucin-containing basal cell carcinomas, and vascular lesions. Compression of vascular lesions can help to distinguish vasculitis from simple telangiectasias. Better margin identification can also be discerned.

Acquired melanocytic naevi on an adult usually look alike. We can call them signature naevi (Figures 7a and 7b). For experienced clinicians, selective dermoscopy prevents unnecessary biopsies, particularly for patients with multiple atypical naevi.²⁸ This assists in identifying a worrisome lesion – the ugly duckling (such as Figure 7c).

Figure 7. (a–c) Most melanocytic naevi on one adult are usually similar. Both (a) and (b) are similar with peripheral globules. The naevus in (c) comes from for the same patient, with a peripheral network seen. This might thus be an ugly duckling. Fortunately, full symmetry in patterns and colours is seen, and biopsy is unnecessary.

Figures 8a and 8b depict a melanocytic naevus on the face. The pattern is a pseudo-network, meaning that the pigmentation spares holes for small and dense hair follicles on the face. A viral wart, as multiple chambers with blood vessels seen inside, is extending from the right upper part to the centre of the naevus. This is therefore a compound lesion with two skin diseases bearing different aetiologies, presentations and management options. Look out for these multiple lesions in numerous combinations.

Figure 8. (a) A melanocytic naevus inferior to the medial canthus of the left eye. (b) Polarised dermoscopic image of the lesion in (a). A pseudo-hyperpigmented network (commonly seen for lentigines and naevi on the face) is present. A warty growth is radiating from the right superior aspect of the naevus. This multi-pathological lesion might be missed by a casual examination of the facial skin.

For taking publishable dermoscopic images, we suggest camera-lens-like dermoscopes (left, Figure 9).

Figure 9. Probably the best set of apparatus for clinical photography and dermoscopy in the present state of technology. Accessories such as lighting systems are not included. We have on the right a high-grade single lens reflex camera with fixed autofocus 105 mm 1:2.8 macro lens, with a set of wireless commander (attached to the hot shoe) and remote flashlights attached to the right and left aspects of the lens. A circular filter is applied. On the left is the same camera body with a lens-shaped dermoscope mounted. A cable transmits the signal from the hot shoe to the dermoscope, leading to alternating captures of images with and without cross-polarisation upon each shutter release. The quality of images can be up to publishable standards.

For clinicians performing dermoscopy frequently, we recommend having two camera bodies – one for clinical photography (right, Figure 9) and the other for dermoscopy (left, Figure 9). This saves precious time otherwise spent on switching lenses, mounting adapters and other equipment, and modifying settings in the camera bodies. The risk of dust and fungal collection inside the cameras is also minimised.

For all clinical and dermoscopic images with a possibility of future publication, especially images on the face or external genitalia, informed consent – preferably written – is necessary. For images of children and adolescents, we strongly advocate seeking informed written consent from the parents or legal guardians.

Dermatopathologists talk about ‘nests’ of melanocytes but what is a nest? Figure 10 demonstrates a polarised dermoscopic image for a lentigine on the scrotal wall. Each pigmented spot denotes one nest of melanocytes. Dermoscopic features of skin diseases seen in this order of magnification – if clinically significant – provide ample opportunities for clinical research.

Figure 10. Polarised dermoscopy with extremely high magnification (~100×) captured images of lentigines on the scrotal wall. One spot represents one nest of proliferating melanocytes. Many clinically significant dermoscopic features at such orders of magnification are likely not to have been published yet.

Take dermoscopic images immediately after the application of intralesional or perilesional anaesthesia. This can offer diagnostic clues of depth and vascular patterns.

Owing to the asymmetry of patterns and colours,^25–27 we decided to biopsy a melanocytic naevus. We applied perilesional anaesthesia, and the lesion ‘floated’ above the deeper tissues but was still attached (Figure 11a). The dermoscopic image (Figure 11b) is crisp and sharp, and of publishable quality.

Figure 11. (a) A melanocytic naevus with chaos to be excised for histopathology. Upon the administration of perilesional local anaesthesia, the lesion was lifted up. (b) Very clear polarised dermoscopic image taken immediately after local anaesthesia of the lesion in (a).

Obviously, this could only be done after the decision to biopsy has been made. The value of this manoeuvre is that the architecture and parameters of lesions are more clearly perceived by clinicians before the surgery.

Figure 12a is a polarised dermoscopic image from a lesion of a patient with alopecia areata. Nothing is missing but a message. We magnified, cropped, augmented and annotated, resulting in Figure 12b. The message of exclamation marks is thus lucid beyond words.

Figure 12. (a) Dermoscopic image of an adolescent with alopecia areata. The figure is of high quality. However, there exists no message. (b) An augmented view of (a). The steps are: (1) locate a suitable site; (2) magnify (crop) digitally; (3) adjust the brightness, contrast, hue and colour saturation; and (4) annotate with red circles. The message of hairs becoming thinner and thinner becomes clear. Atrophy of skin and skin appendages are seen. There is no background inflammation.

Skin cancer is globally on the rise. Early detection is a challenge, even in countries that have health-care systems with adequate economic resources and medical staff.²⁹ Campaigns to raise awareness and foster prevention have been ongoing for more than a decade.^30,31 Due to its superficial growth and natural course in preclinical stages, skin cancer is highly amenable to screening interventions with potential economical and health benefits.^32,33

In many health-care systems, primary care physicians play an important role as the first contact person and a gatekeeper. They are usually aware of skin cancer risk factors such as family history and sun exposure, so they play a key role in the early detection of skin cancer.

In a survey of 500 primary care clinicians,¹⁷ 44.4% felt unsure in detecting potentially malignant lesions, and slightly more declared that they would refer all patients with suspicious skin lesions to dermatologists. In some health-care systems, the time-lags in referral actions are long. These delays can adversely affect prognoses.¹⁸

In contrast, as many as 79% of primary care practitioners expressed the wish for training in the early detection of skin cancer.¹⁷ We thus advocate for more resources to train these clinicians in applying dermoscopy.

The 25 recommendations above are the results of our decades of experience performing dermoscopy in a wide range of clinical settings and in multiple parts of the world. Each one may not be applicable to all clinicians. An example is toggling – we witnessed many clinicians performing such a manoeuvre frequently, while other clinicians found it to be of no impact at all both during the formations of clinical diagnoses and before biopsy. Yet, we would like to share our experience so that more investigators might report their experiences.

To the best of our knowledge, each of these 25 pieces of advice is our original idea or exemplification out of common sense, except for toggling, skin manipulation, selective dermoscopy, signature naevi and ugly ducklings. The toggling and skin manipulation are well-accepted practices. Unfortunately, despite an exhaustive search, we have not been able to find the original publications concerned; however, selective dermoscopy, signature naevi and ugly ducklings have been reported.^3,28

Clinical medicine embraces the virtues of science, technology, art and craft. We believe that craftsmanship plays a predominate part in dermoscopy. Where possible, we substantiate some of the recommendations by dermoscopic images. As to the usefulness of some of our advice, only time can tell.

We thus conclude that our recommendations may enhance the diagnostic accuracy made by primary care physicians when confronted by skin cancer and other skin diseases. Taking into account the prominent role of primary care in most health-care systems, we believe that these recommendations might facilitate the early diagnosis of skin cancer and other skin diseases in many parts of the world.

Apart from such sponsorship, we received no other benefit – financial or otherwise – from these two manufacturers (Dermlite, 3Gen Inc. San Juan Capistrano, CA, USA; and Firefly Global, Belmont, MA, USA). We strongly recommend readers to consider obtaining dermoscopes from all manufacturers, not only from these two brands.