[Utility of next-generation sequencing for diagnosing non-secretory multiple myeloma].

A 62-year-old man was referred to our hospital for leukocytosis with an increase (25.5%) of plasma cell-like cells in the peripheral blood. M-protein was not detected, and no deviation of the κ/λ ratio of free light chain was observed. Bone marrow biopsy showed increased plasma cell-like cell counts; however, immunohistochemical staining was positive only for CD138, and negative for both κ and λ chains. Non-secretory multiple myeloma (MM) was diagnosed based on morphological findings, although differential diagnosis from lymphoplasmacytic lymphoma was difficult. After remission induction treatment, the patient underwent autologous peripheral blood stem cell transplantation and relapsed one year later. The disease was refractory to various chemotherapies. To support the diagnosis, next-generation sequencing was performed on a bone marrow sample obtained at relapse. The analysis showed multiple mutations in driver genes (IRF4, TRAF2 and TRAF3) and 1q gain, which are characteristic of MM. These mutations are associated with a poor prognosis, which is consistent with the clinical course of the present case. This case highlights the potential utility of next-generation sequencing in diagnosis and therapeutic decision-making for MM.