Fig. 1.

The number of HER2-positive breast cancer cases (HER2 3+, HER2 2+/amplified, amplified) per institute of pathology in relation to the number of cases investigated was plotted on a logarithmic scale. The 99.5% confidence interval is indicated by red lines. In institutions with a low number of assessments, the confidence interval is broader. The expected rate calculated from the mean value of 36 institutions within the 99.5% confidence interval is demonstrated by a blue line. There are six institutions outside the 99.5% confidence interval (indicated by red crosses). Four of these potentially underestimate HER2 and two have a higher positivity rate than could have been expected. Institutes with a positivity rate within the 99.5% confidence interval are represented by white circles