Comparative Immunohistochemical Expression of HER2/neu in Intestinal-type and Diffuse-type Gastric Adenocarcinoma: A Cross-Sectional Study
Keywords:
Gastric Adenocarcinoma, Her2/Neu, Immunohistochemistry, Intestinal-Type, Diffuse-Type.Abstract
Background: Human epidermal growth factor receptor 2 (HER2/neu) is a well-known predictive marker of targeted therapy in gastric adenocarcinoma. Local data on the comparison of HER2 expression in intestinal-type and diffuse-type gastric adenocarcinoma are limited.
Objective: To compare the immunohistochemical expression of HER2/neu in intestinal and diffuse-type gastric adenocarcinoma.
Methods: This was a cross-sectional comparative study carried out at Prime Teaching Hospital, Peshawar, from 1st November 2025 to 30th April 2026. Using non-probability consecutive sampling, 106 gastric adenocarcinoma cases, 53 intestinal-type and 53 diffuse-type, were enrolled, all of which were histopathologically confirmed. The independent samples t-test, Chi-square test, and Fisher's exact test were used to compare clinicopathological characteristics and HER2 expression. Odds ratios (ORs) with 95% confidence intervals (CIs) were derived, and values less than 0.05 were deemed statistically significant.
Results: The mean age of the participants was 58.6 ± 11.4 years, and 64.2% of participants were male. The overall HER2 positivity (IHC 3+) was 13.2%. There was a significant difference in the percentage of HER2 positivity between intestinal-type and diffuse-type gastric ADC (22.6% versus 3.8%, respectively; p < 0.001). Patients with intestinal-type tumors had 7.12-fold higher odds of HER2 positivity (OR = 7.12, 95% CI: 1.49–34.01, p = 0.009). HER2 positivity was also significantly associated with lymphovascular invasion (p = 0.043).
Conclusion: HER2/neu overexpression was significantly associated with intestinal-type gastric adenocarcinoma, supporting routine HER2 testing to identify patients who may benefit from targeted anti-HER2 therapy.
