The prognostic dilemma of nodal micrometastases in breast carcinoma.

The presence of axillary lymph node metastasis in patients with breast cancer is a major prognostic factor and also determines the use of adjuvant chemotherapy. Micrometastasis has been arbitrary defined as deposits of < 2 mm dimension. Earlier studies of micrometastases failed to demonstrate prognostic relevance. However, when larger numbers of patients were followed up for longer periods, micrometastasis was shown to be a significantly poor prognostic parameter with patients having a survival rate similar to those with macrometastasis or nodal disease. There are no compelling reasons to retain the term "micrometastasis" in the light of these findings and our understanding of tumor biology. Routine histological examination of axillary lymph nodes is a notoriously inaccurate method for the detection of metastases. When serial or multilevel sectioning and/or immunohistochemical staining for cytokeratin were employed, detection rates increased by as much as 33%. Reverse transcriptase-polymerase chain reaction and Southern blotting for CK19 may be a more accurate method of examination. However, there are inherent technical problems associated with this method, and the recent finding of a pseudogene with great homology to CK19 in normal peripheral blood nucleated cells further emphasises the need for caution in this approach. It is not cost-effective to employ serial sectioning and immunohistochemistry when examining the axillary contents. However, the introduction of sentinel-node biopsy may allow detailed examination of the single node most likely to harbour a metastatic tumor.