The size of a micrometastasis in the axilla in breast cancer: a study of nodal tumour-load related to prognosis.

Much has been written on micrometastases to the axilla in breast cancer but there is no consensus as to their size. In this study three levels of nodal tumour-load are defined following measurement of nodal tumour area on histology. The two cut-points described are both of clinical interest. The smallest deposits, up to 0.0001 cm2, include embolic growth on the afferent side of the node, which is, as reported previously, of poor prognosis. In such cases post-operative prognosis approaches that in the "node-positive", here defined as cases with an axillary tumour-load of 0.5 cm2 or more. Between these two groups is a collection of cases, 40% of the total series, with a prognosis similar to the node-negative. It is suggested that the deposits in this intermediate group should be termed micrometastases, the high risk cases with embolic growth reported as such and those with larger deposits as node-positive.