Fig. 1: Examples of unacceptable HER2 IHC staining in test slides.

A A test slide from Tissue 1 showing unacceptable IHC 1+ staining (200×). B Weak external control for the test slide from Tissue 1 (200×). C IHC 1+ region in a test slide from Tissue 3 (200×). D IHC 2+ region in the same test slide from Tissue 3 (200×). E Tumor heterogeneity observed in the test slide from Tissue 3 (20×). F Weak external control corresponding to the test slide from Tissue 3 (200×).