Manual assessment of HER2 protein expression by immunohistochemistry (IHC) in gastric and gastroesophageal junction (GGEJ) adenocarcinomas is prone to inter-observer variability and hampered by tumor heterogeneity and different scoring criteria. Equivocal cases are frequent, requiring additional in situ hybridization (ISH) analysis. This study aimed to evaluate the accuracy of digital image analysis (DIA) for the assessment of HER2 protein expression. Hundred and ten GGEJ adenocarcinomas were included in TMAs with three tissue cores per case. Two immunoassays, PATHWAY® and HercepTest™, and fluorescent ISH (FISH) analysis were performed. The Visiopharm HER2-CONNECT™ Analysis Protocol Package (APP) was applied through the ONCOtopix™ DIA software platform. HER2 membrane connectivity, calculated by the APP, was converted to standard IHC scores applying predetermined cut-off values for breast carcinoma as well as novel cut-off values. Cases with excessive cytoplasmic staining as well as HER2 amplified IHC negative cases were excluded from analysis. Applying HER2-CONNECT™ with connectivity cut-off values established for breast carcinoma resulted in 72.7% sensitivity and 100% specificity for the identification of HER2 positive gene amplified cases. By application of new cut-off values, the sensitivity increased to 100% without decreased specificity. With the new cut-off values, a 36-50% reduction of IHC equivocal cases was obtained. In conclusion, HER2-CONNECT™ with adjusted cut-off values seems to be an effective tool for standardized assessment of HER2 protein expression in GGEJ adenocarcinomas, decreasing the need for ISH analyzes.
Nielsen SL, Nielsen S, Vyberg M. Digital Image Analysis of HER2 Immunostained
Gastric and Gastroesophageal Junction Adenocarcinomas. Appl Immunohistochem Mol
Morphol. 2016 Oct 31. [Epub ahead of print] PubMed PMID: 27801737.