In that system, hemoglobin, serum calcium, serum M protein, serum creatinine, and number of bone lesions on MRI/positron emission tomography (PET) are used as surrogates to measure myeloma cell mass, because BMPC% by biopsy is unreliable due to the heterogeneous distribution in the skeletal system [37], as suggested in this study. This evidence concerns the gene MYOM2 and plasma cell myeloma.