The predictive pathology in the diagnosis of B-cell lymphomas is a field in evolution. As our understanding of these tumours progresses so does our ability to predict their evolution. This is true not only in the wider and traditional sense where a given marker identifies a group of tumors with a better or worse prognosis but also with reference to specific patients. Here the development of new therapeutic agents whose activity depends on the expression within the tumour of specific proteins has begun to bring the long awaited era of "personalised therapy" a little closer to reality.