The most difficult task for a pathologis is defining the primary focus of the tumour in cases where only a faction of a metastasis is available for examination. Nevertheless, at present, it is feasible to tract the tumour differentiation down and, using antibody battery, parcicularly against specific cytokerines and vimentine and including organ-specific markert, to identify the primary source or at least to establish an assumption about the most likely organ affected by the tumour process.