Detection of breast cancer micrametastases in peripheral blood using immunomagnetic separation and immunocytochemistry

Background: Although there have been many reports on the immunocytochemical detection of bone marrow micrometastases in breast cancer patients, peripheral blood micrometastases (PBM) have rarely been studied by immunocytochemistry (ICC). Methods: PBM in operable and metastatic breast cancer patients were studied using immunomagnetic separation of tumor cells followed by immunocytochemistry (IMS-ICC). Results: PBM were not detected in any peripheral blood samples from 21 healthy women, six patients with benign disease, or in a 21 patients with primary operable breast cancer, of which there were 7 stage I (n=7), 9 stage II, 2 stage Ill, and 3 inflammatory tumors. On the other hand, PBM were detected in 8 of 29 patients with metastatic breast cancers (27.6%). The number of tumor cells per patient varied from 2 to 90 cancer cells (median: 8 cells). Positivity of PBM was not significantly associated with the first site of recurrence, number of involved organs, tumor marker status, performance status, or diseasefree interval, but it was significantly (p<0.01) associated with progesterone receptor negativity. Conclusion: PBM are very rare in primary operable breast cancer patients but can be observed in a considerable number of metastatic breast cancer patients. The clinical significance of PBM still remains to be established.