Staging and follow-up of breast cancer patients. Staging systems for breast cancer, unlike those of neoplasms in distant or recessed sites, allowed for the early development of clinical staging evaluation. It was established that clinical assessment of the breast lesion was often wrong compared with the pathologic examination (benign vs. malignant); clinical measurement of the tumor in centimeters was often larger than histologic size; and clinical assessment of axillary nodes (clear or metastatic) was incorrect in about 30% of cases. Although both clinical and pathologic staging provide effective discriminants for prognosis of treated patients, prognosis is more accurately determined by the pathologic stage. The single most important prognostic indicator is the axillary nodal status, and when positive, the number of positive nodes. The American Joint Committee on Cancer and the Union International Contra Cancer have agreed on a TNM staging for breast carcinoma, and this is the preferable staging system. Follow-up of treated patients is of most value in detecting local recurrence on the chest wall (after mastectomy) or in the irradiated breast (after lumpectomy), and also in early detection of contralateral breast cancer. Physical examination and periodic mammography are most useful. There is a tendency to overinvestigate asymptomatic patients (with bone scans, blood tests, etc.), but this has been correctly criticized in recent years. 