Where are the immunoglobulins? A review of non-secretory multiple myeloma

Multiple myeloma (MM) is a malignant neoplasm of clonal plasma cells, typically associated with the production of a monoclonal protein. In 1–3% of cases, MM presents without measurable monoclonal protein (M protein) in the serum or urine and normal serum-free light chains; these cases are referred to as non-secretory MM (NSMM). This definition has changed over time according to the sensitivity of laboratory methods for detecting paraproteins. NSMM has been previously reported to have a less aggressive presentation and clinical course compared to secretory MM; however, the literature is conflicting. Recent studies have indicated that NSMM may exhibit different responses to therapy and outcomes, emphasizing the need for a tailored approach. This review consolidates the current understanding of NSMM and underscores the importance of advanced diagnostic techniques in improving patient management and outcomes.