High-resolution array-based comparative genomic hybridization for distinguishing paraffin-embedded Spitz nevi and melanomas

Distinguishing between Spitz nevus and melanoma presents a challenging task for clinicians and pathologists. Most of these lesions are submitted entirely in formalin for histologic analysis by conventional hematoxylin and eosin-stained sections, and fresh-frozen material for ancillary studies is rarely collected. Molecular techniques, such as comparative genomic hybridization (CGH), can detect chromosomal alterations in tumor DNA that differ between these 2 lesions. This study investigated the ability of high-resolution array-based CGH to serve as a diagnostic test in distinguishing Spitz nevus and melanoma using DNA isolated from formalin-fixed and paraffin-embedded samples. Two of 3 Spitz nevi exhibited no significant chromosomal alterations, while the third showed gain of the short arm of chromosome 11p. The latter finding has previously been described as characteristic of a subset of Spitz nevi. The 2 melanomas showed multiple copy number alterations characteristic of melanoma such as 1q amplification and chromosome 9 deletion. This study has shown the utility of array-based CGH as a potential molecular test in distinguishing Spitz nevus from melanoma. The assay is capable of using archival paraffin-embedded, formalin-fixed material; is technically easier to perform as compared with conventional CGH; is more sensitive than conventional CGH in being able to detect focal alterations; and can detect copy number alterations even with relatively small amounts of lesional tissue as is typical of many skin tumors.