Pathway her2 4b5

Tissue HER2 status was analyzed by immunohistochemistry (IHC) (clone Ventana pathway HER2 4B5) in all tumors and by in situ hybridization (ISH) for score 2+ tumors by IHC (INFORM HER2 dual ISH DNA probe cocktail, Ventana) according to the ASCO and to experts recommendations [1 (link), 16 (link), 17 ]. The laboratory regularly contributes to the National Breast Pathology External Quality Assessment scheme.

Clinical HER2 status was assessed using dual in-situ hybridization (ISH) and IHC according to Swedish guidelines for HER2 testing in breast cancer [31 ]. The clinical scoring was performed on a separate section, independently evaluated by an experienced bladder and breast cancer pathologist (GC) using Ventana Pathway HER2 4B5 and Ventana Dual ISH assay HER2 DNP and CHR17 DIG probes on the BenchMark Ultra platform. The IHC score (0, 1+, 2+, 3+) was determined by the highest staining observed in >10% of the tumor cells. An ERBB2/CEN17 ISH ratio ≥ 2, or ≥ 4 ERBB2 copies when CEN17 was not determinable, was used for amplification calls. In samples with two TMA cores the highest ratio was used for calling amplifications. HER2 amplified tumors with IHC 2+ scores in > 10% of cells were considered HER2-positive. The inter-observer agreement between the IHC core intensity scores by GS and the clinical re-evaluation by GC was excellent (kappa 0.807 with equal weights).