A new TNM classification for breast cancer to meet the demands of the present and the challenges of the future.

In this article we will describe our proposed changes to the breast cancer tumour nodal metastasis (TNM) classification which, while retaining TNM structure to ensure compatibility is retained, will render it more useful and better able to accommodate future developments. We propose changing T to specify exact tumor size (a tumor of pathological diameter 1.7 cm would be pT1.7); changing N to specify the number of metastatic lymph nodes over the total number removed (e.g., pN5/21); adding suffixes to M to indicate metastatic site; removing in situ neoplasms from the classification, since they are not carcinomas and are incapable of metastasizing; and removing the terms 'infiltrating' and 'invasive' since they are redundant. Finally, we would include hormone receptor, HER2, and other biological indicators of prognosis, as they are verified, in a placeholder system appended to the TNM. These proposals shift the emphasis from the quantity of tumor present to the quality of the cancer.