Dermoscopy (also called dermatoscopy), is an essential tool for dermatologists, plastic surgeons, general practitioners and other health professionals attempting early diagnosis of melanoma. Using dermoscopy to evaluate pigmented lesions, the abnormal structural features of melanoma can be identified, borderline lesions may be closely observed and benign lesions can be confidently diagnosed without the need for biopsy. Dermoscopy is also increasingly useful in diagnosis of non-pigmented skin lesions and inflammatory dermatoses.
Dermoscopy performed by experts results in enhanced accuracy of diagnosis, with increased sensitivity and specificity for the detection of early melanoma.
But dermoscopy is hard! Dermoscopy should never override a strong clinical suspicion of melanoma. Beginner dermoscopists are also likely to overdiagnose melanoma.
What is dermoscopy?
Derm(at)oscopy refers to the examination of the skin using skin surface microscopy, and is also sometimes called ‘epiluminoscopy’ and ‘epiluminescent microscopy’. Dermoscopy is mainly used to evaluate pigmented lesions in order to distinguish malignant skin lesions, such as melanoma and pigmented basal cell carcinoma, from benign melanocytic naevi and seborrhoeic keratoses.
Dermoscopy requirements include a high quality lens for 10 to 14-times magnification and a lighting system. This enables visualization of subsurface structures and patterns. Hand-held devices are usually lightweight and battery-powered.
Fluid immersion and polarised systems are available.
Fluid immersion involves applying mineral oil or spraying alcohol onto the lesion, then placing the lens in contact with the skin. These systems have the advantage of accurate focus but the disadvantage of compressing the vasculature. The plate needs to be cleaned between lesions, and should be sterilised after each patient using alcohol. Alternatively, the lens can be covered with a fresh piece of polyvinyl film (cling food wrap) between each patient.
Polarised lenses do not need to be in contact with the skin. They can be quickly scanned over many lesions. In general, the polarised view is as good as the fluid immersion technique, and may be better for evaluating vessels. However, it may be helpful to wipe a scaly lesion with oil to enhance the view. Surface scale may also be removed by repeated tape stripping.
Effectiveness of dermoscopy
Several studies have demonstrated that dermoscopy is useful in the identification of melanoma, when used by experts.
It may be up to 35% more accurate than clinical diagnosis
It may reduce the number of benign lesions excised
In primary care, it may result in the referral of more suspicious lesions and fewer banal ones
New users may unfortunately become less accurate at diagnosis at first, paradoxically increasing the number of unnecessary excisions.
Convenient attachments to dermoscopy devices allow high quality video or still digital photography, allowing review on a computer screen and comparison with images taken at follow-up appointments.
Dr Fourie uses the DermDoc system with a 30X magnification and polarised lense, connected to a computer, running mapping software in order to map the lesions on a skin map allocated to the patient's name. No oil is needed and the lens makes contact with the skin.
It is estimated that dermoscopy can detect 92% of melanomas immediately because of typical features. The remaining 8% do not have identifying features and are diagnosed because of change in an atypical lesion. Structural change can be detected in superficial melanomas within 3 to 6 months.