Challenges involved in the diagnostic interpretation of FISH for melanocytic neoplasms

At the molecular level, melanoma and nevi exhibit distinct chromosomal copy number aberrations. As a result, the addition of molecular techniques such as FISH may improve the diagnostic procedures for melanocytic neoplasms. FISH probes targeting 6p25, 11q13, 6q23, 9p21, 8q24 and CEP 6 are currently used in the diagnosis of melanoma. While these assays can be of great utility, there are challenges that may emerge in optimizing interpretation. In this review, the authors discuss technical challenges commonly associated with the FISH protocol such as overdigestion, underdigestion and excessive background. The authors also present challenges associated with interpretation of the FISH for chromosomal copy number changes and offer suggestions as to how the effects of these difficulties can be minimized.