Axillary metastasis in breast cancer: when, how, and why?

Axillary metastasis in breast cancer is a time-dependent phenomenon that varies greatly from tumour to tumour. It is discussed in relation to tumour diameter and the growth rate of the tumour cells. It parallels the former but is not directly related to either. A tumour age coefficient (Tac) is presented that demonstrates this lack of interrelationship. Tumour growth in the axillary nodes is progressive and in general mimics the potential tumour load elsewhere in the body. Qualitative rather than quantitative assessment is needed. This can be provided by simple means, using hilar nodal sections from standardised nodal samples. There is, however, as yet no definitive method of predicting the presence/absence of occult distant metastatic spread in either node-negative or node-positive cases. Treatment is thus based on statistical probability, which may or may not be relevant in the individual case.