%0 Journal Article %A MAI YAMADA %A MAKOTO KUBO %A HIDETAKA YAMAMOTO %A NAMI YAMASHITA %A MASAYA KAI %A KAREN ZAGUIRRE %A KAZUHISA KANESHIRO %A AKIKO SHIMAZAKI %A SAORI HAYASHI %A HITOMI KAWAJI %A MASAKI MORI %A YOSHINAO ODA %A MASAFUMI NAKAMURA %T Effect of the 2013 ASCO-CAP HER2 Testing Guideline on the Management of IHC/HER2 2+ Invasive Breast Cancer %D 2021 %R 10.21873/anticanres.15217 %J Anticancer Research %P 4143-4149 %V 41 %N 8 %X Background/Aim: With advances in anti-HER2 treatment and improved prognoses of HER2-positive breast cancer, the American Society of Clinical Oncology and the American Society of Pathologists (ASCO/CAP) have revised the HER2 diagnostic guidelines several times. We examined how to respond clinically to the revisions of the interpretation of the immunohistochemistry (IHC) method. Patients and Methods: We re-evaluated 254 patients diagnosed as HER2 IHC equivocal, who underwent fluorescence in situ hybridization (FISH) before and after the IHC diagnostic criteria update in 2013. Results: Twenty of 131 (15.3%) IHC equivocal cases by the ASCO/CAP 2007 guideline were IHC score 3+ and one of 20 (0.76%) was negative for FISH. Five of 123 (4.1%) IHC equivocal cases by the ASCO/CAP 2013 guideline were negative for IHC as per the 2007 guideline and four were positive for FISH. Conclusion: After revision of the ASCO/CAP 2013 guideline, 3.3% of HER2-negative cases before the revision should have received anti-HER2 treatment. %U https://ar.iiarjournals.org/content/anticanres/41/8/4143.full.pdf