Hypopigmented atypical Spitzoid neoplasms (atypical Spitz nevi, atypical Spitz tumors, Spitzoid melanoma): a clinicopathological update

The clinicopathologic classification, diagnosis, and management of Spitzoid melanocytic lesions is one of the most problematic topics in dermato-oncology and dermatopathology. After earlier anecdotal reports [1,2], the controversial history of these controversial lesions began in 1948 when Sophie Spitz described 13 cases of what she called “juvenile melanoma,” underlining its presumably good prognosis because only one case of her series had proven fatal [3]. During the following forty years, however, the entity described by Sophie Spitz was thought to be completely benign, with metastasizing cases being intuitively considered as cases of melanomas simulating Spitz nevus (Spitzoid melanoma) [4]. In 1989, Smith and co-worker described the so-called “Spitz nevus with atypia and metastasis” or “malignant Spitz nevus,” i.e., a kind of lesion showing histopathologic features not enough for a diagnosis of malignancy, yet capable of nodal metastasis, usually with no further dissemination [5]. This apparently contradictory concept was then set forth by Barnhill with the diagnostic category of “metastasizing Spitz tumor” [6], or “atypical Spitz nevus/tumor” [7]. To date, while some opinion leaders maintain that there are only two diagnostic categories (nevus and melanoma) and that every “abnormal” behavior is simply a diagnostic mistake [8], some others suggest that Spitzoid lesions are indeed a “morpho-biologic spectrum” of lesions ranging from benignity to full-blown malignancy [9], and sharing a peculiar genetic profile, with chromosome rearrangements involving kinase fusions [10]. Intermediate lesions within such a spectrum eventually show: i) an equivocal histomorphology, featuring a diagnostic agreement among experts which is consistently lower than for “conventional” (non-Spitzoid) melanocytic neoplasms [7,11]; ii) peculiar clinical features and behavior with a relatively high incidence in prepubescent patients [12] and a higher incidence of regional (sentinel) node involvement [13] but a better prognosis than “conventional” (non-Spitzoid) melanoma of the same thickness/stage [14] (possible lowgrade malignancies [11]). Hypopigmented atypical Spitzoid neoplasms (atypical Spitz nevi, atypical Spitz tumors, Spitzoid melanoma): a clinicopathological update