The clinicians and pathologists use a number of characteristics to describe properties of tumors, including site, size, extent, histological type and histological grade, etc. The importance of such characteristics or variables lies in their ability to discriminate between subsets of tumors that may have a different outcome.
Some variables have a greater ability for such discrimination.
In general, for a majority of tumors including colorectal cancers, the stage of the tumor is the single most important such variable. The staging of a tumor uses a convention of a shorthand notation to provide a summary of extent of the primary tumor, which can assist the clinicians in planning of treatment and gives an indication of prognosis. Accurate and consistent use of a staging system would also help in evaluation of results of treatment, comparative studies between different centers and on-going investigations of tumor therapy and behavior. The staging of colorectal cancers is complicated by the fact that multiple staging systems are in use and there is no agreement on which staging system should be used. Although most staging systems rely on the depth of tumor invasion and absence or presence of nodal and distant metastases, there is no consensus on how various categories should be grouped.