Gastric Cancer

Definition

Gastric cancer is a malignant neoplasm arising from the lining of the stomach, most commonly adenocarcinoma, with variable presentation depending on tumor location, histology, and stage.

Epidemiology

• Fifth most common cancer worldwide and third leading cause of cancer death
• Higher incidence in East Asia, Eastern Europe, and South America
• Peak incidence: 60–70 years
• Slight male predominance
• Incidence declining in many developed countries but still high in certain regions due to H. pylori prevalence

Etiology

• Helicobacter pylori infection is the most significant risk factor
• Dietary factors: high salt, smoked, or processed foods; low intake of fruits and vegetables
• Genetic predisposition: CDH1 mutation, Lynch syndrome, familial gastric cancer
• Chronic atrophic gastritis, intestinal metaplasia, and pernicious anemia
• Smoking, alcohol, and prior gastric surgery increase risk

Pathophysiology

• Chronic inflammation from H. pylori leads to gastritis, atrophy, intestinal metaplasia, dysplasia, and carcinoma
• Tumor may originate in proximal (cardia) or distal (antrum) stomach
• Histologic types: intestinal type (well-differentiated), diffuse type (poorly differentiated, signet-ring cells)
• Local invasion into muscularis propria, serosa, and adjacent organs
• Spread: lymphatic (regional nodes), hematogenous (liver, lung), peritoneal dissemination