Interphase FISH for Chromosome 1q and 6q

Dual colour interphase FISH was performed on FFPE sections using commercial probe sets. For the evaluation of a potential chromosome 1q gain, a spectrum green labeled probe was used for test locus 1q25.3 and a spectrum orange labelled probe for control locus 1p36.31 (ZytoLight). For the evaluation of a potential chromosome 6q loss, a spectrum green labelled probe was used for test locus ESR1 at 6q25.1 and a spectrum orange labelled probe for the alpha satellite centromeric region of chromosome 6 (D6Z1) (ZytoLight). Signals were scored under a fluorescence microscope in 100 non-overlapping, intact nuclei under oil-immersion. If a cell showed three or more signals of the 1q test probe or the ratio of test probe-control probe inside one nucleus was more than one, signals were scored as chromosome 1q gain. If a cell showed one or less signals of the 6q test probe and/or the ratio of test probe-control probe inside one nucleus was ≤ 0.5, signals were scored as chromosome 6q loss. Tumor signals were scored as gains or losses for the whole area when at least 10% of the cells showed the gain or loss, as previously described [22 (link), 28 (link)].