We present the case of an 81-year-old woman with right shoulder discomfort and right supraclavicular lymph node swelling who referred to our hospital. Blood tests results showed normal immunoglobulin levels, but free light chain assay showed abnormal κ/λ ratio. Serum immunoelectrophoresis detected immunoglobulin G-λ type M proteins. ¹⁸F-fluorodeoxyglucose computed tomography revealed swelling of the right supraclavicular and mediastinal lymph nodes. Biopsy of the right supraclavicular lymph node showed a mixture of small lymphocytes with plasma cell-like round cells that were positive for cell surface CD20, CD138, CD56, IgG and λ, and negative for transthyretin and amyloid A. They had a Congo red stain-positive, glass-like surrounding structure and apple-green birefringence was observed under polarized light. Duodenal, gastric, and skin biopsies also showed amyloid deposits. We diagnosed the patient with lymphoplasmacytic lymphoma complicated by systemic light-chain amyloidosis. Rituximab monotherapy led to complete metabolic response. Systemic amyloidosis is a rare complication of B-cell lymphoma; however, the possibility of amyloidosis should be considered, even in patients with lymphadenopathy.