Spitz Nevus versus spitzoid melanoma - Diagnostic difficulties, conceptual controversies

The histologic distinction of Spitz nevus and Spitzoid melanoma is notoriously difficult, and an additional complication is provided by the fact that there may be a group of Spitz tumors that has the propensity to spread regionally, but not to distant sites. The interpretation of regional spread is subject of controversy. Mones and Ackerman regard it is as formal proof of malignancy, whereas others have argued that this stance constitutes an oversimplification. The ongoing controversy regarding the typing of "difficult" Spitz tumors with regional spread reflects these different viewpoints. We review the arguments that support the notion that regional spread cannot be equated with distant metastasis, and provide a critical commentary on Mones' and Ackerman's interpretation of their data and their review of the relevant literature. We advocate the use of 3 diagnostic categories: Spitz nevus, Spitzoid melanoma, and a provisional group of "Spitz tumor of uncertain malignant potential." A discussion of the pros and cons of different terms and their usage concludes the article.