IMMUNOCYTOCHEMICAL DETECTION OF ISOLATED EPITHELIAL-CELLS IN BONE-MARROW - NONSPECIFIC STAINING AND CONTRIBUTION BY PLASMA-CELLS DIRECTLY REACTIVE TO ALKALINE-PHOSPHATASE

Detection of isolated tumour cells (TCs) in bone marrow (BM) from epit helial cancer patients by immunocytochemical (ICC) analysis seems to p redict future relapse, but the reported percentages of positive BMs am ong patients with localized cancer show large variations and the numbe r of detected TCs is low. This emphasizes the importance of thoroughly testing the methods in use. This study was performed to clarify to wh at extent positive staining of haematopoietic cells (HCs) interferes w ith the ICC detection of epithelial cells in BM, BM mononuclear cells (MNCs) from normal donors and stage I-II breast cancer patients were s tained with anti-cytokeratin (CK) and isotype control monoclonal antib odies (MAbs) followed by alkaline phosphatase (AP)-based visualization of immunolabelled cells. In the ICC staining of normal donors by the anti-CK MAbs AE1/AE3 or A45-B/B3, rare immunoreactive cells were detec ted in 7/20 and 8/19 BMs, respectively. Morphological examination reco gnized all these cells as typical HCs. In the breast cancer patients ( n=257), anti-Ca-positive cells were detected in 26.6 per cent, excludi ng cells with HC morphology, Using the same morphological criteria, is otype control-positive cells were detected in 5.4 per cent of patients . Some of the false-positive events were further analysed and cells wi th strong reactivity against the AP enzyme alone were detected, Double :ICC staining recognized the majority of these AP directly-reactive c ells as CD45-negative and human Ig kappa/lambda-positive, in accordanc e with the phenotype of mature plasma cells. Morphological evaluation and adequate controls are important to ensure the diagnostic specifici ty of micrometastases in BM. It is recommended that the number of BM M NCs included in negative controls should equal the number of cells in the diagnostic specimens, (C) 1998 John Wiley & Sons, Ltd.