Histopathology of Spitz naevi and "Spitzoid" melanomas.

Abstract

The histological distinction between Spitz naevus (Spitz 1948) and a small group of melanomas which resemble Spitz naevus and which are therefore often referred to colloquially as “Spitzoid melanomas” (Smith et al. 1989; Chan et al. 1999) is notoriously difficult and may occasionally be impossible. In the past decades, the recognition of variants of Spitz naevus has resulted in a marked expansion of its clinical and histological spectrum. The differential diagnostic problem is compounded by the fact that like Spitz naevus, Spitzoid melanoma preferentially affects the younger age-groups and may even occur in very young children (Mehregan and Mehregan 1993). In a series of 23 melanomas occurring in children up to 15 years of age, Barnhill (1998) considered three cases to represent Spitzoid melanomas, and a further nine cases were designated “atypical Spitz tumours” (see below), while only six of the cases showed the histology of usual adult-type melanoma. Although there is some evidence to suggest that, as a group, “Spitzoid melanoma” has a more favourable prognosis than other melanomas of similar thickness, there is no doubt that individual examples of Spitzoid melanoma can progress beyond locoregional disease and can kill the patient. A correct diagnosis is therefore of eminent importance. In this brief review, I shall discuss the salient features of Spitz naevi and Spitzoid melanomas, with special emphasis on potential pitfalls and on diagnostically helpful features.