The stomach is the J-shaped organ located in the upper left part of the abdomen. Our stomach is responsible not only for the digestion of food we eat, but it also stores the food temporarily. Our stomach secretes gastric juice, which comprises of water, hydrochloric acid, electrolytes, pepsin, and mucus which helps with the digestion of food. Our body continuously replaces old cells with new cells. Sometimes due to mutations the body isn’t able to replace the old cells, whereas, the new cells continue to form. This abnormal or uncontrolled formation of cells is called cancer. 
Cancer is a life threatening disease because it can damage blood vessels and can cause bleeding. The abnormal or uncontrolled growth of cells in the mucous lining of the stomach leads to stomach cancer. Gastric cancer is also termed as “a silent killer”. This cancer is asymptomatic in the very start, or shows uncharacteristic symptoms which is why it goes unnoticed for a long time before it reaches a critical condition. Mostly when a person is diagnosed with it, the cancer has already invaded other organs. Stomach cancer is ranked 3rd among the cancer related deaths and 6th most common cancer worldwide. Stomach cancer is most common in people with old age, however, it can also occur in adults and children. With the increase in the use of refrigerators and microwave ovens, the cases of gastric cancer have also increased.
There are many types of stomach cancer. 
Carcinoma is defined as the cancer in the epithelial lining. Our stomach is lined with a mucous lining that contains epithelial cells which secrete mucous. Any uncontrolled division in these cells causes stomach cancer. 90% of people diagnosed with stomach cancer fell into adenocarcinoma’s category. Gastric adenocarcinoma is further divided into two types:
The abnormal growth of the cells near the stomach in the small intestines blocks the food from entering into the intestine. The treatment of this type of cancer is fairly easy when compared to diffuse gastric adenocarcinoma.
This type of adenocarcinoma is termed as diffuse because it affects most of the stomach. The major reason behind this type of cancer is genetic mutations, and this is why it is difficult to cure.