Stage IV cancer means that the cancer has moved from the primary location to distant locations in the body, such as lymph nodes, according to the National Cancer Institute. A variety of diagnostic methods, including imaging tests, blood tests and physical exams, are used to determine the stage of cancer.
Not all cancers are classified by the staging system, which is usually used for solid tumor cancers. Some cancers, such as blood cancers and those of the spinal cord, are classified by a different method that uses the cell type and grade. Other methods are used to stage other types of cancers, such as reproductive cancers. According to the American Society of Clinical Oncology, the stage of cancer when it is diagnosed can make a difference in the prognosis of the patient, and it can affect a patient's options for treatment and clinical trials.