The spitz nevus: review and update.

The Spitz nevus is a relatively common skin lesion in children and is less commonly seen in adults. The lesion is defined by the presence of distinctive-appearing spindle or epithelioid cells on light microscopy in a recognizable nevus-like pattern. Spitz lesions share features with melanoma on light microscopic examination. When Spitz features are atypical or typical features are absent, distinction from melanoma can be difficult. A spectrum of pathology of Spitz lesions can be found from lesions that are benign and typical to lesions that are atypical with melanoma-like features and frank melanoma. There is significant interobserver variation in interpretation of Spitz lesions. The lack of uniformly applied criteria for distinction of light microscopic grades and the confusion in diagnostic terminology demonstrate the difficulty in the pathologic interpretation of these lesions. Exciting progress has been made recently in ancillary testing that will likely be helpful in determining in more detail the biologic nature of these lesions, in better differentiating the benign Spitz lesions from malignant lesions, and in eventually improving treatment recommendations.