TNM staging system of colorectal carcinoma: surgical pathology of the seventh edition

There is a need for internationally standardized staging of tumours so that various parameters, such as stage at presentation, can be compared in epidemiological data from different countries and regions and in the study populations in published research studies. These staging systems require periodic revision to improve the robustness of the categories and to take account of any advances in understanding of the tumour biology. However whenever changes are made to a staging system the boundaries between categories may alter and there may be a shift in cases from one category in the previous system into a lower or higher stage in the new system. This can affect the meta-analysis of studies published over a long period of time. This review examines the latest revision of the staging of colorectal cancer and the effects that this may have on the long-term integrity of staging data.