Identification of mammary metastatic cells in the bone marrow as a marker of a minimal residual disease and of their proliferative index as a factor of prognosis--an immunocytologic study with monoclonal antibodies.

A study of 200 patients with breast cancer at different stages was carried out. Proliferating mammary cells in bone marrow were detected using a double-staining method with monoclonal antibodies. Mammary cells were visualized with antibodies raised against human breast tissue or carcinoma. DNA-synthetising cells (S-phase) were detected on the same slide, using the monoclonal antibody antibromodeoxyuridine (BrdU), after cell incubation with BrdU. Mammary cells could be detected in the bone marrow of 60% of the studied cases. In 50% of the samples with such 'micrometastasis', a high labelling index of the carcinoma cells was found. The correlation between the presence of micrometastasis and the general prognosis at the stage of residual disease is discussed.