Rethinking TNM: a breast cancer classification to guide to treatment and facilitate research

The TNM UICC classification of breast cancer categorizes tumor size, regional lymph node involvement, and distant metastases. Treatment is influenced by these characteristics, but requires knowledge of several other factors. In fact, effective treatment is dependent on disease extent, hormone receptor status, and other biologic characteristics of the cancer. We propose a new classification [tumor node metastasis (TNM)] that not only includes relevant biologic characteristics and can expand to include others as they are validated but also specifies tumor size exactly (T2.3 indicates a cancer of maximum diameter 2.3 cm), provides more information on regional lymph node involvement, and specifies the site(s) of distant metastases. We also propose abolishing the term carcinoma for non-invasive neoplastic conditions and the term infiltrating for carcinomas. The new classification is sufficiently similar to the TNM UICC classification to permit valid comparison of patients classified by both systems, but is more logical, provides information useful for guiding therapy, and is flexible enough to satisfy present and future clinical and research needs.