Gastric cancer occurs in the stomach lining. People who have chronic gastrointestinal conditions such as gastritis or H. pylori bacterial infections have a higher risk of developing gastric cancer. People who smoke also have an increased risk. Gastric cancer is divided into five stages, labeled 0 to IV, according to how far the cancer has spread.
Stage 0
Stage 0 of gastric cancer may be thought of as a pre-cancerous stage of the disease. Also called carcinoma in situ, stage 0 is described as the occurrence of abnormal cells in the stomach lining. The cells may or may not progress to stage I gastric cancer.
Stage I
Stage I is the earliest stage of gastric cancer in which the cancer has developed fully. This stage is referred to as either IA or IB, according to the National Cancer Institute. Stage IA is defined as affecting the mucosal wall of the stomach, which is the innermost area of the stomach. Stage IB occurs when the cancerous cells or tumors are located not only in the mucosal layer of the stomach, but also the middle layer called the musclaris. Stage IB also includes involvement of as many as six lymph nodes that are located close to the malignant tumor.
Stage II
A person who is diagnosed with stage II gastric cancer has already experienced some spread of the disease. As many as 15 lymph nodes in the mucosal layer may be affected by the cancer, as well as up to six lymph nodes in the musclaris section of the stomach. The outermost area of the stomach wall, called the serosal layer, is invaded with cancerous cells during stage II.
Stage III
Like stage I, stage III is labeled IIIA or IIIB according to the location of the spreading cancer. In addition to all areas and lymph nodes of the stomach, IIIA describes cancer that has spread to other organs that are close to the stomach. Lymph node involvement in the serosal layer of the stomach is called stage IIIB.
Stage IV
Stage IV is the most advanced stage of gastric cancer that has metastasized to other areas of the body in addition to the stomach and surrounding lymph nodes. The disease may also be diagnosed as stage IV if more than 15 lymph nodes throughout the body are affected.
