Fluorescence in situ hybridization for the differential diagnosis between Spitz naevus and spitzoid melanoma

The differential diagnosis between Spitz naevus and spitzoid melanoma can be extremely difficult, or even impossible. In recent years, many attempts have been made to find specific histopathological or immunohistochemical markers, although none has proved successful. Because the prognosis and treatment of each are very different, it is important to distinguish between these entities. We evaluated the ability of the fluorescence in situ hybridization (FISH) assay-designed to detect the copy number of the RREB1 (6p25), MYB (6q23) and CCND1 (11q13) genes and of centromere 6 (Cep 6)-in order to distinguish between Spitz naevus and spitzoid melanoma.

We evaluated 12 spitzoid melanomas and six Spitz naevi from our records. The diagnosis of both conditions was based on previously described histopathological criteria. We obtained valuable results for FISH in eight spitzoid melanomas and five Spitz naevi. Chromosomal aberrations were detected in seven of the eight spitzoid melanomas (FISH-positive) and in none of the five Spitz naevi. The FISH-negative spitzoid melanoma was the least typical in its group.

FISH was able to distinguish between Spitz naevus and spitzoid melanoma, with a sensitivity of 87.5% and a specificity of 100%. Our findings suggest that FISH could prove a useful tool in the differential diagnosis between these entities.