Evaluation of HER2 by automated FISH and IHC in gastric carcinoma biopsies

Abstract

Purpose: The use of trastuzumab (Herceptin) to target HER2 has been applied in breast carcinoma and gastric carcinoma (GC). Previous studies have tested trastuzumab’s effectiveness by assessing HER2 expression or HER2 amplification by means of immunohistochemistry (IHC) or fluorescence in situ hybridization (FISH). In this work we aimed to evaluate automated FISH and IHC technologies for HER2 detection in GC biopsies to be used in routine pathology practice. Methods: The study used an Oracle HER2 IHC System and an LSI HER2/CEP17 Dual Probe on an automated Bond™ system (Leica Microsystems). One hundred GC biopsies were evaluated including 44 intestinal type, 38 diffuse type and 18 indeterminate type according to Lauren’s classification. Results: The overall concordance rate between the automated FISH and IHC methods was 94% (κ = 0.87), as 6 samples were scored as equivocal (4 in IHC and 2 in FISH). Moreover, HER2 positivity was significantly different between the 3 types of GC (p<0.05), being more frequent in intestinal-type GC (23%) than in the other 2 histological types (5% and 0%). Finally, the HER2/CEP17 FISH ratio was significantly different (p<0.01) between disomic and polysomic samples, being higher in polysomic samples (mean 1.633 ± 0.509) than in disomic samples (mean 1.231 ± 0.675). Conclusions: Automated HER2 testing of GC biopsies using the Leica Bond system was useful and efficient. This method allowed us to improve normal routine procedures, minimizing time and costs as well as handling and observation errors.