The tumor-node-metastasis system is a cancer classifi cation system that is used around the world as a common language to classify anatomic disease extent in tumours. The aims of the TNM staging system were to aid the clinician in planning treatment, to give some indication of prognosis, to assist in the evaluation of the results of the treatment, to facilitate the exchange of information between treatment centres and to contribute to the continuing investigation of human cancer. This system has served oncologists well for more than 50 years. But now questions are being asked about its usefulness in the 21st century. This review discusses some of the limitations of current TNM system and gene expression-based molecular classifi cation of breast cancer.
Keywords: Breast cancer, TNM, Breast cancer classifi cation