[Determination of tumor biological parameters in breast cancer: round robin testing for quality assurance].

Round robin testing for quality assurance in the determination of the breast cancer biomarkers estrogen receptor (ER), progesterone receptor (PR) and epithelial growth factor receptor 2 (HER2) have been carried out in Germany for 13 years. As the first quality assurance trial worldwide tissue microarrays with 20 different breast cancer specimens were used. As a further innovation the challenges were split into a test part representing routine cases and a training part enriched with difficult borderline cases in order to uncover latent weaknesses in the participating laboratories. Certificates are issued based exclusively on the test part. Similar to NordiQC and UKNequas stained slides are assessed externally and the quality of staining and evaluation are considered separately. Since 2010 an additional internet-based trial without assessment of the staining quality is offered for ER and PR. Since the introduction of the round robin trials the numbers of participants (n = 200-250) and the success rates have steadily increased. The breast cancer quality assurance trial ranks first with regard to the number of participants in Germany. It could be demonstrated that regular participation in the round robin test leads to an improvement of staining results of ER, PR and HER2 and hence appears to be mandatory for maintaining quality standards. The use of fully automated immunohistochemical staining procedures has steadily increased and these are now used by approximately 50 % of participants.