The reliability of HER2-status determination from core-needle-biopsies and surgical specimens: A comparison of two established test methods (IHC, CISH)

e22141 Background: A milestone of breast-cancer therapy was the discovery of HER-2 entailing special targeted therapy with improved prognosis. The HER-2-status is routinely assessed through immunohistochemistry (IHC; HercepTest) showing protein over-expression and is double-checked with in-situ-hybridisation (ISH) demonstrating gene amplification in equivocal cases. It is questioned whether these methods achieve identical results in core-needle-biopsies and in excisional tumor specimens. Methods: We performed a retrospective comparative study in order to address these questions. From 01/03–06/08 we collected the HercepTest results from both core-needle-biopsy and surgical specimen of 109 breast cancer patients in our institute and compared these to newly evaluated chromogenic ISH (CISH) results for both specimen types in order to assess the reliability of HER-2- diagnosis of both methodological approaches and of specimen type. Results: We found no significant difference in the HER- 2-status determined from either needle-biopsies or surgical specimens irrespective of the test used. For the overall comparison (218 specimens) of HercepTest and CISH we found only slight, non-significant deviations. Four cases were CISH-negative in spite of HercepTest scoring of 3+. Vice versa, five out of the total of 38 (17.4%) CISH-positives did not correspond to the HercepTest results of 0 or 1+. Conclusions: Though not significant, there is some inconsistency in the HER-2-determination depending on the test-method, leaving these cases equivocal. In accordance with the literature, we therefore recommend to at least double-check samples with 2+ in the HercepTest as it is the current standard. Our data support the use of core-needle-biopsy as a reliable tissue sample for HER-2-diagnosis. [Table: see text]