Whereas the causes of stomach cancer are not clearly understood, risk factors for cancer have been studied extensively. These include faulty dietary habits like high salt intake, preserved meat, lifestyle habits like smoking, obesity, environmental factors like infection by Helicobacter pylori, Epstein Barr virus. Medical conditions like pernicious anemia, gastroesophageal reflux, gastric polyp also increase the risk of gastric cancers. Certain genetic risk factors predispose to stomach cancer increase the risk of familial gastric cancer.

If identified in early stages, stomach cancer is curable and in very early stages, it is possible to remove it by endoscopic techniques like endoscopic mucosal resection or submucosal dissection in selected individuals.

Cure in cancer is stated as 5-year survival. When cancer is confined to the stomach, the 5-year survival nearly reaches 70%, but once it spreads to adjacent areas or lymph nodes this drops to about 30%. With the advent of multimodality treatment including chemotherapy, radiotherapy and precision oncology, the survival and quality of life have been increasing.

Stomach cancer spreads to lymph nodes around the stomach and from thereon to the next level of lymph nodes with key blood vessels supplying the stomach and adjacent organs. Spread beyond these lymph nodes is considered as the distant spread.

Another common area of spread beside adjacent organs like the intestine and pancreas is to the abdominal cavity and its lining producing deposits and fluid within the abdomen called ascites. These are advanced forms of cancer.

The commonest type of stomach cancer is carcinoma, arising from the rapid multiplication of the cells lining the stomach wall. Other less frequent tumours include lymphoma, gastrointestinal stromal tumour, neuroendocrine or carcinoid tumour.