Stomach cancer begins when cancer cells form in the inner lining of the stomach and then grow uncontrollably.
Gastric carcinoma is the most frequent malignant tumor of the stomach; it usually grows slowly over many years.
In recent decades, the incidence of cancer in the main part of the stomach (body of the stomach) has decreased worldwide, but meanwhile, cancers in the area where the upper part of the stomach meets the lower end of the esophagus (gastroesophageal junction) have become much more common.