Interlaboratory concordance in HER2 testing: Results of a Serbian ring-study.

Purpose: The purpose of this study was to assess the immunohistochemistry and chromogenic in situ hybridization (CISH) inter-laboratory consensus between national pathology laboratories in Serbia.

Methods: This study was conducted between 2013 and 2016. In 2013, HER2 results were evaluated using two sets of four different breast cancer specimens in five laboratories.