ABSTRACT
The T, N, and M classifications are separately defined for tumors at each anatomic site. Although TNM staging offers a valuable platform for assessing tumors at most sites, certain cancers require a different approach to staging. Both Hodgkin’s and non-Hodgkin’s lymphoma, for example, are staged by distribution and symptomatology, rather than local extent of the disease. Primary tumors of the central nervous system have not been amenable to TNM staging. In the brain, the size of the tumor is not as important for outcome as the histology and location. There are no lymph nodes in the brain, so an ‘‘N’’ classification is not possible. Finally, most patients with brain cancer tend to have a short survival time, so distant metastases do not have time to develop or cannot pass through the blood-brain barrier.
