Although HER2 overexpression and Her2 amplification have been noted in breast and a variety of human cancers, we report here for the first time the impact of polysomy-17 on HER2 status and the correlations between HER2 status and other prognostic factors in patients with epithelial ovarian cancers (EOC).We analyzed HER2, estrogen receptor (ER), progesterone receptor (PR), p53, and Ki-67 protein overexpressions by immunohistochemistry (IHC) and determined Her2 gene amplification by fluorescence in situ hybridization (FISH) in 27 tissue microarray samples from EOC patients.We achieved 100% positive concordance (3/3) and 100% negative concordance (19/19) between HER2 testing by IHC and FISH. Both the total Her2 gene copies and FISH scores increased significantly in a stepwise order through the negative, equivocal, and positive HER2 IHC result categories in all 27 cases (P=0.001, P=0.001), and still increased significantly in 18 nonpolysomy-17 cases (P=0.007 and 0.013) after the exclusion of 9 polysomy-17 cases. HER2 protein expression is inversely correlated with both ER (P=0.002) and PR expressions (P=0.046). Her2 gene amplification is inversely correlated with ER expression (P=0.007) but not with PR expression (P=0.106).This study showed extremely high positive and negative concordances between Her2 FISH and HER2 IHC assays. Polysomy-17 is insufficient for causing a significant impact on the relationship between HER2 testing by IHC and FISH in EOC. ER and PR expressions were inversely correlated with HER2 protein expression. In addition, ER but not PR expression is inversely correlated with Her2 gene amplification.