2017 Volume 66 Issue 5 Pages 500-507
<Objectives> The American Society of Clinical Oncology/College of American Pathologists guideline was revised in 2013 (2013 ASCO/CAP guideline). The aim of this study is to elucidate how the 2013 ASCO/CAP guideline affects current clinical breast cancer practice. <Methods> From April 2014 to March 2016, we collected the results of HER2-FISH tests for breast cancer by biopsies from 226 cases. On the basis of the 2013 ASCO/CAP guideline, we reevaluated the results of HER2-FISH tests and compared them with those of original reports. We also investigated the results of immunohistochemical analysis of estrogen receptor (ER), progesterone receptor (PgR), and HER2. <Results> Of the 226 cases, 37 (16.4%) were determined as positive on the basis of the 2013 ASCO/CAP guideline. Two of the 37 positive cases had HER2/CEP17 ratios of less than 2.0, but HER2 copy numbers were more than 6.0, which were previously negative. Twenty-four (10.6%) cases were equivocal. Among these cases, 3 were triple negative [ER (−), PgR (−), HER2 (−)] breast cancers. <Conclusions> The 2013 ASCO/CAP guideline increased the number of additional positive and equivocal cases in HER2-FISH tests, which were diagnosed as negative on the basis of the previous guideline. A non-negligible number of cases became equivocal on the basis of the 2013 ASCO/CAP guideline. In addition, 3 (12.5%) cases that were diagnosed as “triple negative” on the basis of the previous criteria might be candidates for HER2-targeted therapy if diagnosed on the basis of the 2013 ASCO/CAP guideline. Our data suggest that the 2013 ASCO/CAP guideline can increase the number of patients receiving HER2-targeted therapy.
