In a series of 300 patients operated for a cancer of the breast the internal and external mammary chain have been removed. The extemporaneous analysis has enable us to verify and complete the data collected at the clincial exmination. By this mean, we have selected on objective criteria the most favorables cases for conservative surgery. The histological examination of the lymph nodes shows a stricking relation between the T. and the N. This confirms the clinical conclusions. Finally we have shown that the appreciation of the T is of the outmost importance to predict an eventual envolvement of the internal mammary chain.