HER2 Oncogene Amplification and Immunohistochemical Profiling in Gastric Adenocarcinoma.

Background and Objectives: Gastric adenocarcinoma is one of the most common malignant tumors and a major cause of cancer death worldwide, especially in developing countries. Her2/neu gene amplification and protein overexpression in breast cancer is a golden criterion for the targeted therapy with trastuzumab. However, the role of Her2 as a prognostic factor in gastric cancer is still controversial. The purpose of this study was to evaluate the frequency of Her2 oncogene overexpression and concordance between the results for Her2 protein expression and gene amplification. Materials and Methods: A total of 65 retroprospective cases with gastric adenocarcinoma, including biopsy and resected specimens obtained between July 2015 to December 2017, were analyzed. Her2/neu expression was determined by Immuno-histochemistry (IHC). Equivocal and some selected cases were submitted for FISH to detect Her2/neu gene amplification. Results: In the present study, out of 65 patients of gastric adenocarcinoma, there were 50 males and 15 females, with mean age of 54.52 years. The majority of tumors were located within the antropyloric region. We found 27 (41.4%) positivity, scored as IHC 3+ and IHC 2+, and 38 (58.3%) negativity, scored as IHC 1+ and IHC 0. We also evidentiated a significant difference between Her2/neu expression with age (p=0.010) and depth of invasion (p=0.020).Her2/neu gene was amplified only in 13 cases, 4 cases were of Her2/neu (3+) positive, 11 cases (39.3%) Her2/neu (2+) with IHC staining. The concordance rate between the results of IHC and FISH in all 18 cases was 83.3%. Conclusion: IHC detection can be carried out to guide the treatment when FISH detection cannot be performed. Overexpression of Her 2/neu in gastric adenocarcinoma could potentially be used in selecting the patients who can get benefit from the anti-Her2/neu targeted therapy.