Spitz naevus: histological features and distinction from malignant melanoma.

Spitz naevus is a benign lesion that can be confused histologically with malignant melanoma. Some malignant melanomas also have an appearance similar to a Spitz naevus. Spitz naevus commonly occurs in children but also occurs in adults. The typical Spitz naevus has a classical histological appearance. This paper reviews several studies which have attempted to develop criteria to separate malignant melanoma and Spitz naevi. Histological features that suggest a diagnosis of malignant melanoma rather than atypical Spitz naevus include deep and marginal mitoses, atypical mitoses, asymmetry, pleomorphism and prominent epidermal involvement.