Representative examples of dual-color interphase FISH images on paraffin sections in chordomas. Detected by the co-hybridization of SpectrumOrange labeled EGFR DNA probe (red signals) and SpectrumGreen labeled chromosome 7 CEP probe (green signals). (A) Case 1a, showing EGFR disomy. (B) Case 10a reveals EGFR polysomy. (C) Case 20 shows low level amplification in < 10% of nuclei. Of note, this amplification is not detected by aCGH. (D) Case 12b, showing high level amplification of EGFR in > 40% of nuclei.