Fig. 1

a HER-2 IHC (2+) of the core needle biopsied tissues of the primary tumor (IHC, *200). b Amplification of HER-2 gene (HER-2 gene/CEP17 ratio: 2.34) detected by FISH in core needle biopsied tissues of the primary tumor (green spots represent signals of centromeric chromosome 17 while red ones stand for that of HER-2 gene). c HER-2 IHC (−) of the surgically excised primary tumor after neoadjuvant chemotherapy (IHC, *200). d HER-2 gene of the surgically excised primary tumor after neoadjuvant chemotherapy was not amplified (HER-2 gene/CEP17 ratio: 1.88, the average number of HER-2 gene per cell: 4.73) as determined by FISH. e HER-2 IHC (−) of the synchronous metastatic axillary lymph nodes after neoadjuvant chemotherapy (IHC, *200). f HER-2 gene of the synchronous metastatic axillary lymph nodes was amplified (HER-2 gene/CEP17 ratio: 2.21) as determined by FISH. Intratumoral heterogeneity was indeed evaluated by observing the distribution of HER-2 gene within tumoral histological sections by fluorescent microscopy. The two signals were scattered in distribution without focal concentrations and clusters, showing no obvious spatial heterogeneity of HER-2 gene. One hundred cells of the tumoral histological sections were analyzed for HER-2 gene positivity. The total number of HER-2 gene signal and the average number of HER-2 gene that each cell harbored were counted and so were for CEP-17. HER-2 gene/CEP-17 ratio was calculated. According to the updated 2013 CAP/ASCO guideline on HER-2 testing [27], HER2/CEP17 ratio cutoff for amplification of HER-2 gene was lowered to ≥ 2.0 and an average HER-2 gene copy number criterion for amplification of HER-2 gene (≥ 6.0/cell) was introduced. FISH testing protocol were obtained from Beijing GP Medical Technologies, Ltd./China Medical Technologies Inc. Beijing, China