Gastric cancer includes tumors of the stomach and esophagogastric junction, with rising incidences in Japan and South Korea, and declining rates in the United States and Europe. Early-stage gastric cancer often presents with nonspecific symptoms, while late-stage symptoms may include gastric outlet obstruction, weight loss, and vomiting, with adenocarcinomas being the most common type. Diagnosis is confirmed through biopsy during endoscopy, and treatment options include surgical resection, chemotherapy, and possibly radiotherapy depending on the cancer's stage.