Stomach cancer develops in the glandular tissue that lines the inner surface of the stomach. It’s most common in the United States, but other types of cancer can affect the stomach as well including lymphoma and sarcoma.
Symptoms of stomach cancer vary and may include stomach pain, loss of appetite and weight loss. Blood in the vomit or bowel movements can also occur. If the cancer has spread to other organs, symptoms such as enlarged liver or jaundice, fluid accumulation in the spaces between tissues and organs in the abdomen and bone fractures may develop.
The most common type of cancer that affects the stomach is called adenocarcinoma. It starts in the glandular cells that line the inside of the stomach and spreads to other parts of the body. This type of cancer accounts for 95 percent to 100 percent of all cases of stomach cancer.
Other types of cancer that affect the stomach are less common and include gastrointestinal stromal tumors (GISTs) that start in immature cells in the wall of the stomach, neuroendocrine tumors and a rare form called linitis plastica, which develops in connective tissue surrounding the mucosa.
Staging describes how far the cancer has penetrated into the layers of the stomach wall and determines how it should be treated. Different types of cancer have different staging systems, but most stomach adenocarcinomas are staged according to the TNM system. T stands for tumor and N is for lymph nodes, and M is for metastasis.
The staging process can be complicated for stomach cancer, because it is difficult to tell how deeply the tumor has penetrated into the tissues of the stomach wall. A doctor will look for signs of the disease on physical examination and perform imaging tests such as X-ray, CT scan or positron emission tomography (PET).
Adenocarcinomas that have penetrated to the inner layer of the stomach are classified as stage I. This stage is less serious because the tumor has not yet reached the lymph nodes or other organs.
For adenocarcinoma, the degree to which the cancer cells are abnormal is used to determine its grade and determine how quickly it will likely spread. Highly abnormal-looking cells are considered poorly differentiated and more likely to spread.
Adenocarcinomas that are poorly differentiated have a higher risk of spreading to other areas of the body, but more-well-differentiated tumors tend to grow more slowly and are less likely to spread. A smear test can be used to assess the degree of differentiation of stomach cancer. The cells are stained with a special stain, which shows the presence of certain proteins. A positive smear test is considered evidence of cancer in the stomach and a good indicator of whether chemotherapy will be effective.
