Cell type, exact size of malignment lesion, presence of multiple tumors in breast, size and number of lymph nodes involved (including micrometastases), extension to adjacent tissues (muscle, fascia, skin).
Sentinel lymph node biopsy
Selective removal of one or more axillary lymph nodes identified by placing dye or a radioactive agent in the tumor bed and following the flow of the dye to specific lymph nodes. The lymph nodes which trap the dye or radioactivity are the first nodes in the lymphatic drainage of the tumor and as such are more likely to contain metastases if present. If the sentinel lymph nodes are negative, there is a 95% chance that all other axillary lymph nodes are negative also.