N3 category in the TNM classification of breast cancer needs to be defined more precisely

When a group of patients having breast cancer metastases only in the internal mammary lymph nodes (Ax-IM+) were compared with those having axillary lymph nodes metastases alone (Ax+IM-) there was no statistically significant difference in the 10-year survival rates (49.3% and 53.2% respectively, p> 0.05). Only where patients have metastatic involvement of both internal mammary and axillary lymph nodes (Ax+IM+) is there a worse prognosis. These data suggest that the TNM breast cancer classification should be modified with the N3 category being restricted to patients with both internal mammary and axillary node involvement.