Carine Ngo1, Marick Laé2, Julia Ratour2, Frédérique Hamel2, Corinne Taris2, Martial Caly2, Annie Le Cunff2, Fabien Reyal3, Youlia Kirova4, Jean-Yves Pierga5, Anne Vincent-Salomon2. 1. Institut Curie, service d'anatomie et de cytologie pathologiques, 26, rue d'Ulm, 75005 Paris, France. Electronic address: carine2708@gmail.com. 2. Institut Curie, service d'anatomie et de cytologie pathologiques, 26, rue d'Ulm, 75005 Paris, France. 3. Institut Curie, service de chirurgie oncologique, 26, rue d'Ulm, 75005 Paris, France. 4. Institut Curie, service d'oncologie radiothérapie, 26, rue d'Ulm, 75005 Paris, France. 5. Institut Curie, service d'oncologie médicale, 26, rue d'Ulm, 75005 Paris, France.
Abstract
INTRODUCTION: The implementation of an internal quality control is mandatory to guarantee the accuracy of HER2 status in invasive breast cancers. OBJECTIVES: To evaluate the impact of our quality control assurance on HER2 status results in invasive breast carcinomas from 2008 to 2014. METHODS: HER2 status was determined by immunohistochemistry as the first-line indication, completed by fluorescence in situ hybridization (FISH) for scores 2+ by immunohistochemistry. Internal quality control of HER2 status relied on the standardization of pre-analytical phases, the use of external controls with a known number of HER2 gene copies determined by FISH and continued monitoring of concordance between immunohistochemistry and FISH. RESULTS: The proportion of HER2-positive cases corresponding to scores 3+ by immunohistochemistry and 2+ amplified by FISH varied from 10.6% to 13.8% (median of 11.3%). The proportion of scores 2+ amplified by FISH varied from 13.3% to 32.7% during period of study. The rate of concordance between FISH and immunohistochemistry for score 0/1+ and 3+ cases were≥97%. Eight among 12 discordant cases were false positive resulting from errors in interpretation of immunohistochemistry (score 2+ instead of 3+). DISCUSSION: Calibration of immunohistochemistry on FISH for HER2 status contributes to limit variability of immunohistochemistry results due to technical issues or interpretation. The implementation of an external control of score 3+ on each slide enables accurate interpretation of score 2+ and 3+ by immunohistochemistry.
INTRODUCTION: The implementation of an internal quality control is mandatory to guarantee the accuracy of HER2 status in invasive breast cancers. OBJECTIVES: To evaluate the impact of our quality control assurance on HER2 status results in invasive breast carcinomas from 2008 to 2014. METHODS: HER2 status was determined by immunohistochemistry as the first-line indication, completed by fluorescence in situ hybridization (FISH) for scores 2+ by immunohistochemistry. Internal quality control of HER2 status relied on the standardization of pre-analytical phases, the use of external controls with a known number of HER2 gene copies determined by FISH and continued monitoring of concordance between immunohistochemistry and FISH. RESULTS: The proportion of HER2-positive cases corresponding to scores 3+ by immunohistochemistry and 2+ amplified by FISH varied from 10.6% to 13.8% (median of 11.3%). The proportion of scores 2+ amplified by FISH varied from 13.3% to 32.7% during period of study. The rate of concordance between FISH and immunohistochemistry for score 0/1+ and 3+ cases were≥97%. Eight among 12 discordant cases were false positive resulting from errors in interpretation of immunohistochemistry (score 2+ instead of 3+). DISCUSSION: Calibration of immunohistochemistry on FISH for HER2 status contributes to limit variability of immunohistochemistry results due to technical issues or interpretation. The implementation of an external control of score 3+ on each slide enables accurate interpretation of score 2+ and 3+ by immunohistochemistry.
Keywords:
Breast cancers; Cancers du sein; Contrôle qualité; Fluorescence in situ hybridization; HER2; Hybridation in situ en fluorescence; Immunohistochemistry; Immunohistochimie; Quality control