TNM, sixth edition: new developments in general concepts and rules.

This article describes changes and clarifications in the 6th edition of TNM that concern site-independent rules, regarding such aspects as sentinel lymph node biopsy, methods to distinguish between micrometastasis and isolated tumor cells, classification of tumors undergoing treatment, tumor deposits in lymph drainage beds, the number of lymph nodes needed for pathologic classification, and classification of residual tumor. These changes mainly reflect advances in diagnosis and treatment, and modulate rather than change the basic rules of classification.