Diagnosis and management of smoldering multiple myeloma: the razor’s edge between clonality and cancer

Smoldering multiple myeloma (SMM) is a rare plasma cell disorder, and as the disease is asymptomatic, diagnosis is often incidental. SMM is characterized by increased marrow infiltration by clonal plasma cells and/or elevated serum M-protein in the absence of a myeloma-defining event (MDE). In recent years, SMM has gained increased attention owing to a broadening of the criteria for MDE, which include apart from the CRAB criteria, three additional parameters. Survival advantage may be offered by early treatment in the high-risk subset, based on a single trial. In this review, we assess the risk factors and models for progression to multiple myeloma. A review of our diagnostic and management approaches to SMM is presented.