Tumour markers (TM) are a group of various molecules which are associated with malignant processes. These markers include enzymes (e.g.
NSE, PSA, thymidinkinase), immunoglobulins (paraproteins), hormones (e.g. hCG, PTH, prolactin), framgents of glycoproteins (e.g. CA 19-9, CA 15-3, CA 125), framgents of cytokeratines (TPA, CYFRA21-1), oncofoetal antigens (AFP, CEA), receptors (oestrogen and progesterone receptors, receptor for IL-2, HER2/neu) and circulating cell elements.