Gastric cancer begins in the inner lining of the stomach and grows slowly over many years. Risk factors include infection with H. pylori bacteria, smoking, diet high in smoked foods, and family history. Early gastric cancer is diagnosed via endoscopy with biopsy. Advanced cancer signs include weight loss, abdominal pain, and vomiting. Treatment involves surgical resection of different extent depending on tumor stage, with some candidates for endoscopic mucosal resection. Adjuvant chemotherapy provides a survival benefit but side effects are common.