The aim of this study was to conduct immunohistochemical examinations of cell and tissue material compared with clinical examinations of markers to discover the possible mechanisms that can result in marker concentration increases in the plasma and other body fluids. From cell material and biopsies it was possible to identify in small-cell carcinomas TPA (52% of the carcinomas), NSE (57%) and no CEA. Of the non-small cell carcinomas (squamous cell and adenocarcinomas) 88% were TPA-positive, 52% CEA-positive and in metastases 100% TPA-positive and 66% CEA-positive. NSE was not found. Marker examinations in tissue and cell material can yield satisfactory results in recognising neuroendocrinal differentiations, and in diagnosis and differential diagnosis of metastases and lymphomas, compared with clinical tumour marker studies.