The Impact of 2013 Updated ASCO/CAP HER2 Guidelines on the Diagnosis and Management of Invasive Breast Cancer: A Single-Center Study of 1739 Cases

The 2013 guidelines increase the detection of HER2+ cases, without introducing significant difference in discordance rate of the IHC and FISH assays. Inclusion of HER2 copy number criterion does not increase the number of FISH equivocal cases in our cohort. We recommend IHC 1+ cases should be offered reflex FISH testing because failure to test them will miss a small number (5%) of potentially treatable cases.