Figure 2

(a) chromogenic in situ hybridisation (CISH) on a breast carcinoma with normal HER2 copy number (1000×). An average of two darkly brown staining copies of the HER2 gene can be seen in each tumour cell. (b) CISH on a breast carcinoma with low level HER2 gene amplification (1000×). An average of 6 copies of the HER2 gene can be seen in each tumour cell. (c) CISH on a breast carcinoma with high level HER2 gene amplification (1000×). Large clusters of darkly brown staining HER2 copies can be seen in each tumour cell. It is not possible to count the exact number of HER2 gene copies; this is the usual result seen in tumours with high HER2 gene amplification.