Surgical pathological staging of breast cancer by sentinel lymph node biopsy with special emphasis on the histological work-up of axillary sentinel lymph nodes.

Axillary nodal status assessed by traditional histological methods is a proven independent prognostic factor in breast cancer. Sentinel lymph node biopsy is a surgical pathologic staging procedure that not only allows the selective removal of the most likely sites of lymphogenic metastases, but also enables upstaging of breast carcinoma by detecting nodal involvement undetected by standard methods of nodal staging. This review highlights the upstaging potential of sentinel node biopsy. It also suggests that incomplete reporting of the pathological methods may make the comparisons of results from different studies difficult. The article also describes a few methods that have been claimed optimal but are probably not, and it formulates basic considerations for building up a histological protocol that can identify all metastases larger than 2 mm, which are of unquestionable prognostic relevance. These considerations are also useful for the detection of micrometastases. Issues of pathological reporting of sentinel nodal findings are also highlighted, with emphasis on the lack of standardization and on the differentiation of isolated tumor cells from micrometastases. Finally the stepwise building up of our current histology protocol and our experience gained since the introduction of sentinel node biopsy in 1997 is also briefly summarized.