Loss of 1 copy of chromosome 3 is considered a significant indicator of metastatic dissemination in uveal melanoma. Fresh or paraffin-embedded tumor tissue is most commonly used for current cytogenetic techniques for determining chromosome 3 status in uveal melanoma and often requires referral to an external specialist laboratory for analysis.
To assess the chromogenic in situ hybridization assay for detecting chromosome 3 alterations using frozen tumor imprints and to compare the results obtained with those obtained by standard fluorescence in situ hybridization or single-nucleotide polymorphism array techniques.
Chromogenic in situ hybridization was performed on 52 frozen uveal melanoma tumor imprints. The genetic status of 26 of the 52 cases had been determined previously by fluorescence in situ hybridization (group 1); the status of 26 cases had been determined using single-nucleotide polymorphism array (group 2).
Chromogenic in situ hybridization was successfully performed on 48 of 52 tumor imprints. Chromogenic in situ hybridization showed excellent agreement in all 24 cases determined by fluorescence in situ hybridization (100% concordance; κ = 1; P < .001; 95% confidence interval, 100%-100%), and disagreed in 4 of the 24 cases previously studied by single-nucleotide polymorphism array (83% concordance; κ = 0.67; P < .001; 95% confidence interval, 95%-39%). All 4 discordant cases were classified as disomic for chromosome 3 by chromogenic in situ hybridization and monosomic by SNP array. On histologic examination, the 4 discordant cases corresponded to 2 mixed cell tumors and 2 spindle cell tumors.
Chromogenic in situ hybridization using tumor imprints is a reliable technique for determining chromosome 3 status in uveal melanoma. Furthermore, it can also be easily integrated into a routine histopathology laboratory.