Smoldering multiple myeloma (SMM) is an asymptomatic plasma cell disorder defned in 1980 by Kyle and Greipp on the basis of a series of six patients who met the criteria for multiple myeloma (MM) but whose disease did not have an aggressive course . At the end of 2014, the International Myeloma Working Group (IMWG) updated the defnition, and SMM defned as a plasma cell disorder is now characterized by the presence of ≥3 g/dL serum M-protein and/or 10–60% bone marrow plasma cells (BMPCs), but with no evidence of myeloma-related symptomatology (hypercalcemia, renal insuffciency, anemia, or bone lesions (CRAB)) or any other myelomadefning event (MDE) . According to these recent update criteria, the defnition of SMM excludes asymptomatic patients with BMPCs of 60% or more, serum free light chain (FLC) levels of ≥100, and those with two or more focal lesions in the skeleton as revealed by magnetic resonance imaging (MRI). Kristinsson et al., based on the Swedish Myeloma Registry, has recently reported that 14% of patients diagnosed with myeloma had SMM, and, accordingly, the agestandardized incidence of SMM would be 0.44 cases per 100,000 people.