Beta-2 microglobulin (B2M) test is used as a tumour marker for some blood cell cancers. It is not diagnostic for a specific disease, but it has been associated with the amount of cancer present (tumour burden) and more importantly can give the healthcare professional additional information about someone's likely prognosis. A B2M test may also be requested to help determine the severity and spread (stage) of multiple myeloma and may sometimes be requested to evaluate disease activity and the effectiveness of treatment. Rarely, a CSF B2M test may be requested to assess central nervous system (brain) involvement.. Beta-2 microglobulin (B2M) is a protein that is found on the surface (part of MHC class I) of almost all cells in the body and is shed by cells into the blood, particularly by B lymphocytes and tumour cells.. "tests done. IGS PP SFLC LDH B2 Microglobulin Ive had a google and they look like tests looking for the signs of cancer to me. Shes very sharp and is now worried that there is something seriously wrong with her despite the fact she feels fine in herself..