Gastric cancer is a major health burden worldwide. It is the second cause of cancer deaths after lung cancer. 1, 2 More than 90% of the tumors are adenocarcinomas, the main focus of this review. The prognosis is dismal, with an average 5-year survival rate of less than 20%, mainly because of late diagnosis, because the early stages are clinically silent. Only a few countries, especially Japan, have set up extensive programs of early detection. If the tumor is detected and treated before it invades the muscular layer of the stomach, the 5-year survival rate can reach 90%. 3 The highest incidence rates are reported for East Asia (Korea, Mongolia, Japan, and China) with annual incidence rates between 40 and 60 per 100,000 inhabitants. In Latin America, pockets of high risk are reported in the Andes Mountains, with rates between 20 and 30 per 100,000, 1 in contrast to the much lower rates reported for the coastal and river valley regions. 4 Lower rates are found in Africa (~ 0.3 to 3 per 100,000, and in affluent populations of North America). The incidence rate in African Americans is about double that seen in white American. In general, the incidence rate for men is double that for women. 1

In recent decades, there has been a gradual decrease in gastric cancer rates in many populations. It has been proposed that this decrease reflects trends in food handling, especially refrigeration and the abundance of fresh fruit and vegetables in the diet, as well as a decrease in the use of tobacco and dietary salt. However, not all types of gastric cancer are declining; tumors of the cardia and esophagogastric junction are becoming more frequent. Recently, an unexplained increase in gastric cancer incidence in younger individuals, mostly less than 40 years of age, has been reported. 5