Lymph node metastasis is one of the most important prognostic factors in breast cancer. Survival of patients with axillary node positive breast cancer is worse than that of patients with axillary lymph node negative breast cancer. Recently, some authors suggest that axillary dissection may be avoidable if sentinel nodes of the breast cancer do not harbour metastasis. However, 15-20% of patients with lymph node negative breast cancer recurs within 10 years. Micrometastasis, which was missed or not detected in routine histologic examination, is thought to be one of the reasons for recurrence of axillary node negative breast cancer patients.

We investigated the frequency of micrometastasis and any clinical significance of micrometastasis in the breast cancer by immunohistochemical staining with anti-cytokeratin antibody from July, 1996 to November, 1990. 70 patients who underwent curative resection for axillary node negative breast cancer were studied retrospectively. We used paraffin blocks of lymph nodes which did not show metastasis by conventional pathological examination. After preparation of tissue blocks with a serial sectioning technique, specimens were stained by an immunohistochemical method using anti-cytokeratin antibody. Hematoxylin-eosin stainings were also repeated. We define metastasis less than 2mm as a micrometastasis.

The results showed that micrometastasis were found in 8 of 70 cases(11.4%). There was a significant relationship between the micrometastasis and tumor size. With median follow-up of 20 months, we found 3 recurrences in 70 patients.: 2 recurrences(3.2%) in the 62 axillary node negative breast cancer patients and 1 recurrences(12.5%) in 8 micrometastasis patients.

The results showed that micrometastasis of lymph node in breast cancer might increase the rick for development of breast cancer recurrence. But, there was no significant relationship between the micrometastasis and recurrence of breast cancer because of small numbers of recurrences and relatively short follow-up period. Long tern follow-up will be needed for further evaluation.