A case of atypical ("pagetoid") compound Spitz nevus on the face of a 2-year-old girl is reported with a review of the literature. The nevus was composed of broad but laterally demarcated compound proliferation of enlarged fusiform and epithelioid melanocytes, with florid pagetoid scatter above the junction. Immunohistochemical analyses revealed the Ki-67 proliferation index to be relatively low. Given the histomorphological overlap with melanoma, an array-based comparative genomic hybridization approach revealed a subthreshold gain in chromosome 1q and gain in distal chromosome 17q, with no other associated chromosomal gains or losses. These molecular aberrations suggested a partially transformed tumor, without adequate evidence for a molecular diagnosis of melanoma. Because of the diagnostic dilemma posed by these lesions, recent research has focused on molecular alterations that may help differentiate Spitz tumors from malignant melanomas.
Keywords: atypical Spitz nevi; comparative genomic hybridization; histomorphology; malignant melanoma; pagetoid.