CD38 and monoclonal gammopathy: In line with CD38 strong expression in MM, literature data described higher BM plasma levels of ADO in MM patients as compared with asymptomatic monoclonal gammopathies as MGUS and SMM; moreover, ADO levels correlated with International Staging System (ISS) staging in patients with active disease suggesting that ADO is produced in the MM niche by an ectoenzymatic CD38 network [79].