Detection of circulating tumor cells and micrometastases in Stage II, III, and IV breast cancer patients utilizing cytology and immunocytochemistry

Evaluation for circulating tumor cells and bone marrow micrometastases has generated considerable interest due to a potential association with disease recurrence and poor prognosis. In this study, we examined bone marrow and apheresis samples from Stage II, III, and IV patients (n 120) enrolled in various clinical breast cancer trials at the National Institutes of Health/National Cancer Institute. For each patient sample, two Diff‐Quik‐stained cytospins were reviewed for morphology, and approximately 1 × 106 cells were analyzed for the expression of cytokeratins using an avidin‐biotin immunoperoxidase method. Keratin‐positive malignant cells appearing as single cells or in small clusters were detected in bone marrow samples from Stage IV patients only (9/68, 13%) and detected in apheresis samples from both Stage III and IV patients (13/245, 5%). These findings indicate that the combination of cytomorphology with immunocytochemistry can be utilized for the investigation of circulating tumor cells and bone marrow micrometastases, and that positive results appear to correlate with high tumor stage/burden. Diagn. Cytopathol. 2000;22:323–328. Published 2000 Wiley‐Liss, Inc.