Immunohistochemical labeling index in breast cancer after in vivo administration of bromodeoxiuridine

Cell kinetics have been classically investigated by thymidine Labeling Index (LI). Recently, S-phase fraction of neoplastic cells has been evaluated by in vivo incorporation of bromodeoxyuridine (BRDU), a thymidine analogue, in dividing cells. In several neoplasms, in vivo administration of BRDU can provide prognostic information regarding the tumour growth. In order to establish the feasibility and the usefulness of this analysis in breast cancer, we determined the in vivo BRDU-LI in 28 patients with locally advanced tumours, using an immunohistochemical technique. The intravenous infusions of BRDU- labeled cells were demonstrated satisfactorily by indirect peroxidase method. BRDU-LI resulted by the radio between labeled and neoplastic cells in more then forty 100x microscopic fields randomly analyzed. Six out of 28 patients failed to yield analyzable data. Mean BRDU-LI of 22 evaluable samples was 2.0 ranging between 0.6% and 5%. All analyzable specimens showed a clear uptake of BRDU by neoplastic cells with a diffuse and homogeneous nuclear staining. Labeled cells were uniformly distributed in the tumour tissue, whereas no BRDU incorporation was observed in two normal tissue samples. BRDU-LI resulted significantly higher in aneuploid than in diploid tutours. No relationships between BRDU-LI and cytofluorimetric S-phase fraction, oestrogen and progesterone receptor status, grading, tutour size and number of involved nodes have been observed. immunohistochemical determination of BRDU-LI provides a simple and useful method to achieve information about cell kinetics in breast cancer.