Gastric cancer is a group of diverse range of malignant tumors arising anywhere in the stomach with the capability of spreading through circulating blood and lymph to different body tissues. Out of the four histological layers of stomach, adenocarcinoma is the most common (90%-95%) form of gastric cancers arising from the epithelial glands of the intimate gastric lining. Involvement of the immune cells in the development of gastric cancer which is usually known as the lymphoma of the stomach comprises of around 4% of all cases, gastrointestinal stomal tumor arising from the connective tissue of the stomach is a rare benign or malignant tumor, another rare form of gastric cancer of neuroendocrine nature known as gastrointestinal carcinoid tumor (3%) develops from the hormone-forming cells in the stomach.

Gastric cancer is the sixth most prominent cancer in the world, accounting for 5.7% of all cancers and has affected 1033701 people worldwide in the year 2012. Gastric cancer prevalence on the whole is higher in East Asia, South America and east Europe, and is less frequent in North America, Africa and eastern Mediterranean region. This region wise variation relies in the diversity in eating practices, and the occurrence of Helicobacter pylori infection. In 2012 gastric cancer took a death toll of 723,000 ranking it third prevalent reason for death world over without gender disparity