Table S1. Clinicopathological characteristics and sample distribution by site Table S2. Primers/probes design for ddPCR (ESR1, EIF2C, AP3P1) Table S3. Raw nanoString counts Table S4. Normalized copy number calls (ER+ samples) Table S5. Normalized copy number calls (ER- samples) Table S6. DdPCR analysis of cell lines Table S7. NanoString raw counts (cell lines) Table S8. NanoString copy number calls (cell lines) Table S9. Nanostring log2 normalized counts (cell lines) Table S10. ESR1 CN amplifications by site in ER- samples Table S11. Multiple Fisher exact comparisons Table S12. ESR1 5`-3` copy number imbalance Table S13. Correlation matrix of ESR1 copy number calls by the different exons and mRNA expression Table S14. Normalized copy number calls for other genes (ER+ samples) Table S15. Normalized copy number calls other genes (ER- samples)