Dear missyh12, An axillary mass might be a swollen lymph node which can swell for various reasons such as infection. It does not have to be breast cancer, however, breast cancer can spread to the axillary lymph nodes, and a mass can develop.
When cancer is staged during surgery the axillary nodes are checked, and on of the criteria used to stage the disease is the number of positive lymph nodes and the size of the positive nodes. If the axillary mass has developed later and it is found to be cancer then this would be recurrent cancer and treated based on that.
if a woman has an axillary mass at the time of the treatment of the original cancer, and if the mass is cancer spread there from the breast, then the cancer is stage two at least. If the axillary mass represents nodes that have fused together from tumor involvement, then it's stage three. As stated above, not all axillary masses are due to cancer, even if a person has cancer in the breast.