The stage of a cancer is a term used to describe its size and whether it has spread beyond its original site. Knowing the extent of the cancer helps the doctors to decide on the most appropriate treatment.

A commonly used staging system is described below. You may find it helpful to refer to our diagram of the stomach wall when reading this section:

Stage 1A The cancer is contained within the inner lining of the stomach (mucosa) only.

Stage 1B The cancer has spread through the mucosal layer of the stomach either to the muscle layer, OR it is affecting up to six of the nearby lymph nodes.

Stage 2 The cancer has spread through the mucosa and is affecting between seven and 15 lymph nodes nearby, OR it is affecting the muscle layer and up to six lymph nodes, OR it has spread to the outer layer of the stomach (serosa).

Stage 3A The cancer has spread to the muscle layer of the stomach and also to between seven and 15 lymph nodes nearby, OR it has spread to the outer layer of the stomach and is affecting up to six lymph nodes, OR it has spread to structures close to the stomach but not to any lymph nodes or any other parts of the body.

Stage 3B The cancer has spread to the serosa and it is also affecting between seven and 15 lymph nodes.

Stage 4 The cancer has spread to organs close to the stomach and to at least one lymph node, OR to more than 15 lymph nodes, OR it has spread to other parts of the body such as the lungs. This is known as secondary cancer (or metastatic cancer).

If the cancer comes back after initial treatment it is known as recurrent stomach cancer.

The grade of a cancer gives an idea of how quickly it may develop. To find the grade of your cancer, your doctors will look at a sample of the cancer (a biopsy) under the microscope. The cancer will be graded as:

• Grade 1 (low grade) – the cancer cells tend to be slow growing, look quite similar to normal cells (are 'well differentiated') and are less likely to spread.
• Grade 2 (moderate grade) – the cells look more abnormal.
• Grade 3 (high grade) – the cancer cells tend to be more quickly growing, look very abnormal (are 'poorly differentiated') and are more likely to spread than low-grade cancers.