Implementation of American Society of Clinical Oncology/College of American Pathologists HER2 Guideline Recommendations in a Tertiary Care Facility Increases HER2 Immunohistochemistry and Fluorescence In Situ Hybridization Concordance and Decreases the Number of Inconclusive Cases

Context.-The American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) guideline recommendations from January 2007 identified many sources of immunohistochemistry (IHC) testing variation. Objective.-In this current study, we implemented the guidelines and addressed our institution's preanalytic, analytic, and postanalytic variables relating to HER2 testing to improve clinical outcomes. Design.-We evaluated core biopsies performed on breast lesions from 2006 through 2007. Prognostic/predictive markers obtained by IHC were correlated with HER2 fluorescence in situ hybridization (FISH). Preanalytic sources of biopsy testing variation were studied by collecting data on the number of biopsies that needed repeat testing because of inconclusive FISH results. Results.-In the year preceding implementation of the guidelines, the HER2 IHC and FISH concordance was 98%. In an additional 10.8% of cases, the FISH results were in-conclusive. When additional material became available to retest the inconclusive cases, the results were informative. Further evaluation of the inconclusive cases revealed that the core needle biopsies received, on average, 4 hours of formalin fixation. After implementation of a minimum 6 hours of fixation and the ASCO/CAP guideline recommendations, the HER2 IHC and FISH concordance was 98.5%. The number of FISH inconclusive cases decreased from 10.8% to 3.4% (a 64% reduction). Repeat estrogen-receptor IHC requests decreased by 40% from 38 in 2006 to 23 in 2007. Conclusions.-We have shown that standardized fixation and adherence to the ASCO/CAP guidelines for HER2 testing has resulted in a greater HER2 IHC and HER2 FISH correlation, decreased numbers of inconclusive FISH cases, decreased repeat estrogen-receptor requests, and financial savings to the Department of Pathology. (Arch Pathol Lab Med. 2009; 133: 775-780)