Beta-2-microglobulin (B2M) is a component of MHC class I molecules,which are present on the surface of nearly all nucleated cells. It can be found in body fluids under physiologic conditions as a result of shedding from cell surfaces or intracellular release. B2M has various biological functions,including antigen presentation. Investigations reveal that increased synthesis and release of B2M are present in several malignant diseases.