When a person is diagnosed with stomach cancer, doctors figure out how far the tumor has grown into different parts of the stomach wall and whether it has spread to nearby tissues or organs. This process is called staging. The stages range from 0 (carcinoma in situ) to 4. The lower the stage number, the less the cancer has spread.
In stage 0, abnormal cells are found in the innermost layer of the stomach wall, called the mucosa. These cells may grow and form a cancerous tumor that has not spread to nearby tissue. Doctors might use a special tool to take a small sample of tissue from the stomach wall to look for cancer cells.
The cells can also be tested under a microscope to see how fast they are growing and if they have any other characteristics that might help predict how quickly the cancer might spread. The results are combined to create a stage number based on the type of tissue affected and the location in the stomach wall.
Most people with stage 1 stomach cancer have a tumor that has grown into the layers of the mucosa and is close to the layer of muscle called the subserosa. But the tumor has not yet reached nearby lymph nodes or other areas of the body.
In this stage, doctors might use other treatments before surgery to try to shrink the tumor and make it easier to remove. These might include chemotherapy or radiation therapy. They might also give the person medications to relieve symptoms. This treatment is called neoadjuvant therapy. Staging might be done again after this treatment to see how well it worked.
Stage 2 stomach cancer has grown deeper into the layers of the stomach wall and might have spread to nearby lymph nodes or other areas of the belly. At this stage, it might be hard for a surgeon to completely remove the stomach tumor and might affect nearby tissues and organs.
In stage 3 stomach cancer, the tumor has grown through all the layers of the stomach and into the lining around the organs in the belly (the peritoneum). At this point, the cancer might have spread to distant parts of the body.
Doctors might use imaging tests to see how far the cancer has spread, including CT and positron emission tomography (PET). They might also need to do surgery to get a closer look at the stomach wall for signs of any small bits of cancer that might have gotten into the liver or belly. These pictures are used to create a staging number that tells doctors how advanced the cancer is and what the best treatment might be. Stage 4 stomach cancer is when the cancer has spread to other parts of the body, usually to the lungs or liver. This is also called metastatic cancer. People with stage 4 cancer might have a combination of treatments to try to lengthen their life and control symptoms.
