INTERLABORATORY CONCORDANCE IN HER-2 POSITIVE BREAST CANCER.

Accurate assessment of HER-2 status is essential for identifying patients who will benefit from HER-2 targeted therapy. The aim of the present study was to show results on the concordance between local and central laboratory testing results in HER-2 positive breast cancer patients. In cases with discordant findings, the immunohistochemical (IHC) and/or in situ hybridization (FISH/SISH) analysis was performed in central laboratories. A total of 104 out of 143 (72.72%) breast carcinoma cases were HER-2 positive (score 3+), while nearly 14% of tumors (20/43) showed weak (score 2+) and 12% (19/143) negative IHC staining (score 0 and 1+). After repeated IHC and ISH, 88% (126/143) were classified as HER-2 positive and 12% (17/143) as HER-2 negative cases. The results obtained are in agreement with many studies that confirmed similar discordance in HER-2 testing by IHC and/or FISH between local and central laboratory. Thus, our findings as well as those from other studies support the importance of regular quality assessment of the staining procedures performed and consistency of interpretation of HER-2 test results.