The competent sentinel node: an association with an axillary presentation and an occult or a small primary invasive breast carcinoma.

The concept of the sentinel node describes a primary or sentinel lymph node (SLN), which exists and through which tumour cells from a primary tumour in a particular location must first travel to spread to a particular regional lymph node group. In this series we present three patients presenting with a pathological axillary node associated with either an occult or very small primary breast cancer. In each case the primary tumour was found to have metastasised to the palpable node, however despite the significant enlargement of this node, no other axillary nodes were found to be affected on axillary node clearance. This has led us to postulate that the SLN in some cases contains unique characteristics that enable it to prevent further spread of the tumour up the lymphatic chain. Hence the term the competent sentinel node.