The goal of this cross-sectional study is to evaluate epigenetic modifications in gastric carcinogenesis, mainly in H. pylori gastritis vs gastric carcinoma. The main question[s] it aims to answer are:

• How does H. pylori infection cause gastric cancer?
• Can DNA methylation and other epigenetic changes predict and affect the development of gastric cancer? Formalin-fixed-paraffin-embedded tissue specimens will be obtained and reviewed for comparison between epigenetic changes in H. pylori gastritis and gastric adenocarcinoma.

Inclusion Criteria:

• Resected specimens and endoscopic guided biopsies of intestinal type gastric carcinoma, H. Pylori associated gastritis, and non-H. Pylori gastritis with:
• Available full clinical data: (age, sex, complaint, findings in clinical examination).
• Full data of previous endoscopy and radiology.

Exclusion Criteria:

• Cases of diffuse type gastric carcinoma.
• Any case of gastric cancer, H. Pylori associated gastritis, non-H. Pylori gastritis, benign gastric lesions with missing clinical, endoscopic, radiologic or follow-up data.
• Cases with no available H&E stained slides or formalin fixed paraffin embedded block.

Formalin-fixed-paraffin-embedded tissue blocks from resected specimens and endoscopic guided biopsies of intestinal type gastric carcinoma, H. Pylori associated gastritis, and non-H. Pylori gastritis.