The lymph nodes status is one of the most important prognostic factors in breast cancer. The routine hematoxilin-eosin staining is efficient for the metastases detection only when there is a large number of tumor cells, while a small number of metastatic cells can easily remain undetectable. For those situations, the immunohistochemistry for cytokeratins, markers of the epithelial cells, is a very sensitive method. We have investigated the cytokeratin 8 expression in 10 primary breast carcinomas and in the corresponding axillary lymph nodes, comparing with hematoxilin-eosin. The routine examination has detected axillary lymph nodes metastases in six cases, confirmed by the immunohistochemistry for cytokeratin 8. Four cases were diagnosed as negative for the axillary lymph nodes metastases by the hematoxilin-eosin staining. In all those four cases, immunohistochemistry for cytokeratin 8 has detected a small number of tumor cells, either spread in the lymph nodes tissues, either confluent as small islets.