Consensus panels in America (AJCC) and Europe (UICC) have established staging systems for head and neck squamous-cell cancers. These staging systems attempt to standardize clinical trial criteria for research studies, and attempt to define prognostic categories of disease. Squamous cell cancers of the head and neck are staged according to the TNM classification system, where T is the size and configuration of the tumor, N is the presence or absence of lymph node metastases, and M is the presence or absence of distant metastases. The T, N, and M characteristics are combined to produce a “stage” of the cancer, from I to IVB.