EVALUATION OF HER2/NEU STATUS IN GASTRIC CARCINOMA USING IMMUNOHISTOCHEMISTRY AND FISH TECHNIQUES

Background:Gastric carcinoma remains a major global health concern, with a high mortality rate due to late diagnosis and limited targeted therapies. Overexpression or amplification of the HER2/neu (Human Epidermal Growth Factor Receptor 2) gene has been identified in a subset of gastric cancers and is associated with aggressive tumor behavior and poor prognosis. Accurate determination of HER2 status is essential for selecting patients eligible for HER2-targeted therapy. This study aims to evaluate HER2/neu expression in gastric carcinoma using Immunohistochemistry (IHC) and confirmatory Fluorescence In Situ Hybridization (FISH) techniques. Materials and Methods: A total of 60 histologically confirmed gastric carcinoma cases were retrospectively analyzed. Formalin-fixed paraffin-embedded (FFPE) tissue sections were subjected to HER2/neu IHC staining. Scoring was done according to the modified Hofmann criteria for gastric cancer. Cases showing IHC scores of 2+ (equivocal) or 3+ (positive) were further evaluated using FISH to assess HER2 gene amplification. Results:Out of 60 cases, HER2/neu overexpression (IHC 3+) was observed in 12 cases (20%), while 18 cases (30%) showed equivocal staining (2+). Negative expression (0 and 1+) was seen in 30 cases (50%). Among the 18 equivocal cases, FISH detected HER2 gene amplification in 10 cases (55.6%). Overall, HER2 positivity confirmed by either IHC 3+ or FISH amplification was noted in 22 cases (36.7%). HER2 positivity was more frequent in intestinal-type gastric carcinoma and tumors located at the gastroesophageal junction. Conclusion:HER2/neu expression is present in a significant proportion of gastric carcinoma cases, highlighting its potential as a therapeutic target. Combining IHC with FISH provides a more reliable assessment of HER2 status, especially in equivocal cases. Routine evaluation of HER2 is recommended in gastric cancer for better prognostication and treatment planning.