Micrometastases to axillary lymph nodes from carcinoma of breast: Detection by immunohistochemistry and prognostic significance

Metastases to axillary lymph nodes is an important factor in predicting prognosis and survival in primary operable carcinoma of the breast. A series of post mastectomy lymph nodes (150 cases) was selected in this retrospective study, in which the initial diagnosis had been no metastases by light microscopy and in which a long follow-up was available (average 10 years). The original H&E sections from these cases were immunostained to detect metastases which might not have been previously appreciated. The study was performed using a cocktail of 5 monoclonal antibodies directed against epithelial antigens. The object was to explore the possibility of detection of occult micrometastases by immunohistochemistry and to evaluate their prognostic significance. Micrometastases with individual cells and cell clusters were readily detected by this technique in 14% of all cases. It also became apparent towards the end of the study that micrometastases could be detected with equal sensitivity by any one of the 5 monoclonal antibodies. Positive staining of malignant cells was found to be more frequent in invasive lobular carcinoma (ILC) than in invasive ductal carcinoma (IDC). However, for the IDC group a striking association was found between micrometastases and both recurrence and survival rate. The ILC sample was considered too small for meaningful interpretation. We recommend the use of immunohistochemical techniques using monoclonal antibodies for the detection of occult metastases in lymph nodes to improve the prediction of recurrence and survival in invasive ductal carcinoma of the breast.