The sample was scored twice by two independent technicians at the Cytogenomics Core Laboratory (Brigham and Women’s Hospital, Boston, MA) for ERBB2:CEP17 ratio in ten different regions identified visually by a pathologist as tumor cell-enriched areas and confirmed by staining with S100A1, a marker that differentially identifies ovarian carcinoma cells from normal ovarian tissue27 (Supplementary Fig. 5A). Here, ERBB2 is linked to ovarian carcinoma.