The TNM staging system.

The new TNM staging system for cancer has great importance because of its applicability for imaging techniques, particularly clinical staging by EUS. The close correlation between clinical (EUS) and pathologic staging permits clinicians to define the strategy for treatment based on the stage of the cancer. In cases where lymph node metastasis is suspected, EUS-guided FNA can be performed for confirmation of this diagnosis by cytology. In the era of minimally invasive surgery, EUS will become the most important diagnostic modality for defining early stage malignant disease. In such cases endoscopic or surgical resection can be performed. When a tumor is shown by EUS to be nonresectable, it will become important to avoid explorative surgery. Despite some limitations, both the TNM classification and EUS clinical staging will be used with increasing frequency in the clinical management of patients with cancer. Furthermore, refinements in the TNM staging system, such as adoption of subclassifications of early cancers and clarification of the definition of regional lymph node involvement, will be necessary to optimize clinical staging. Technologic improvement of EUS instruments, particularly in miniaturization of the echoprobe, will improve the integration of EUS as a routine procedure for cancer staging.