An important prognostic factor in breast cancer is the status of the internal mammary lymph nodes, that is, whether there is tumour in the nodes near the middle of the chest.

These nodes are less accessible than axillary lymph nodes and less likely to be visualised with radioisotope mapping or to be biopsied.

Models to predict metastasis in these lymph nodes have been developed on the basis of anatomy and tumour biology. These will assist cancer clinicians to make decisions about treatment when the status of these lymph nodes is not known.