Dermoscopy and its role in diagnosing melanocytic lesions: a guide for pathologists

Dermoscopy (surface microscopy) is a clinical technique which uses a hand-held magnifying instrument, usually with liquid at the skin-instrument interface, to examine pigmented lesions on the skin surface. A magnification of x10 is usually used. Dermoscopy assists in deciding if the lesion should be excised or biopsied, requires monitoring or can be safely left in situ. The technique provides a bridge between the naked eye appearance of a lesion and the histopathological examination. Multiple dermoscopic features have been described and many of their histological correlates have been determined. Dermoscopic diagnosis usually involves a two-step procedure. The first step is to decide if the lesion is melanocytic or not. If melanocytic, the second step is to decide if the lesion is benign or malignant. Multiple algorithms have been developed to help in this decision. Dermoscopic criteria have been developed for melanoma and naevi. Several non-melanocytic pigmented lesions can be diagnosed with dermoscopy, including pigmented basal cell carcinoma, seborrhoeic keratoses, haemangioma and lichen planus-like keratosis.