After the determination is made as to the type of cancer, the cancer is graded -- a measurement of how aggressive the tumor is. Most cancer cells are graded by how much they look like normal cells. Grading is done in the lab using cancer cells taken during biopsy.
Cancers are usually graded from low to high. Low-grade cancers look more like normal tissue under the microscope. High-grade tumors look very abnormal and are generally more aggressive with a poor outcome.
Once cancer is diagnosed, more tests will be done to find out the size of the tumor and whether the cancer cells have spread to other parts of the body. This testing is called staging. To plan treatment, a doctor needs to know the stage of the disease. Stage refers to the extent, or the size, of the cancer and whether it has spread from where it started. Each cancer, by organ, has its own staging system. In most cases, stage is labeled with 0 and Roman numerals I through IV, with stage IV being the highest stage.
Stage 0 or carcinoma in situ. Carcinoma in situ is very early cancer. The abnormal cells are found only in the first layer of cells of the primary site and do not invade the deeper tissues.
Stage I. Cancer involves the primary site, but has not spread to nearby tissues.
Stage II. Cancer has spread to nearby areas but is still inside the primary site.
Stage III. Cancer has spread throughout the nearby area.
Stage IV. Cancer has spread to other parts of the body.
Recurrent. Recurrent disease means that the cancer has come back (recurred) after it has been treated. It may come back in the same area or in a different part of the body.
Higher numbers usually mean more extensive disease, larger tumor size, and/or spread of the cancer beyond the organ in which it first developed to nearby lymph nodes and/or nearby organs. Once a stage is assigned and treatment given, the stage is never changed. For example, if a stage I cancer of the cervix is treated, and 2 years later a metastasis (spread of the same cancer) is found in the lung, it is not now stage IV, but remains a stage I, with recurrence to the lung. However, some cancers may be restaged.
The important thing about staging is that it determines the appropriate treatment, helps doctors provide a prognosis, and allows for comparison of treatment results between different treatments.