Cancer staging can be divided into a clinical stage and a pathologic stage. In the Tumor, Node, Metastasis system, clinical stage and pathologic stage are denoted by a small "c" or "p" before the stage. This staging system is used for most forms of cancer, except brain tumors and hematological malignancies. Clinical stage is based on all of the available information obtained before a surgery to remove the tumor. Thus, it may include information about the tumor obtained by physical examination, blood tests, radiologic examination, biopsy, and endoscopy. Pathologic stage adds additional information gained by examination of the tumor microscopically by a pathologist after it has been surgically removed. Because they use different criteria, clinical stage and pathologic stage often differ. Pathologic staging is usually considered to be more accurate because it allows direct examination of the tumor in its entirety, contrasted with clinical staging which is limited by the fact that the information is obtained by making indirect observations of a tumor which is still in the body. However, clinical staging and pathologic staging often complement each other.