Dermatoscopic pitfalls in differentiating pigmented Spitz naevi from cutaneous melanomas

Epiluminescence microscopy (ELM, skin surface microscopy, dermoscopy, derma toscopy) is a valuable method for improving the diagnostic accuracy in pigm ented skin lesions. Specific ELM criteria are already recognized for differ entiating pigmented Spitz naevi (PSN) from cutaneous melanomas (CM). Our pu rpose was to describe the ELM appearance of a series of PSN with emphasis o n PSN and CM with overlapping features. Thirty-six consecutive patients wit h PSN, and three cases of CM (selected from a larger database) exhibiting E LM 'spitzoid' features, were evaluated clinically, dermatoscopically and hi stopathologically. Most PSN (27 of 36; 75%) displayed two typical ELM patte rns, namely the starburst (19 of 36; 53%) or the globular pattern (eight: o f 36; 22%), which were correlated to different histopathological findings, in nine of 36 (25%) PSN, atypical ELM features which are more commonly seen in CM were observed. These PSN with an atypical pattern were characterized by an uneven distribution of colours and structures, and an irregular diff use pigmentation resembling blue-white veil or irregular extensions (black blotches). These atypical lesions mostly occurred in children and showed no history of growth, In contrast, in three examples of CM, the typical ELM c riteria of malignancy were less recognizable and either the characteristic starburst or globular pattern usually seen in PSN was present, These three lesions occurred in adults and had a recent history of change in colour, sh ape or size. The overlap in ELM features of some PSN and CM represents a ma jor diagnostic pitfall when ELM examination is considered alone. In these a typical cases, clinical history including the age of the patient may be the only clue to enable a correct diagnosis.