Monocyte-derived giant cell formation in patients with breast cancer.

Recent reports of monocyte-derived giant cell formation in breast cancer and associated retroviral findings have attracted much interest in the scientific literature and with the media, revitalising hypotheses of a viral role in the aetiology of the disease. We describe an assay developed to investigate further the giant cell forming phenomenon and report results which conflict with earlier work. We observed a smaller proportion of patients with breast cancer forming giant cells than in previous reports. Conversely, a much larger proportion of controls formed giant cells. Using our assay to calculate a fusion index the formation of giant cells, as defined in earlier work, was found to be a poor indicator of the degree of cell fusion in our samples. We discuss our experiences with the assay and suggest the calculation of a fusion index as a more comparable and quantitative measurement of cell fusion.