A 43-year-old man presented with lower abdominal pain. Initial values of laboratory examinations were as follows: white blood cells (WBC), 8.62×10⁹/L; hemoglobin (Hb), 11.4 g/dL; platelets, 268×10⁹/L; serum calcium, 9.1 mg/dL; protein/albumin, 6.7/4.5 g/dL; and creatinine, 3.4 mg/dL. Abdominopelvic computed tomography (CT) revealed osteolytic lesions in the right 6^th rib and right ilium. Serum protein electrophoresis (PEP) showed no specific finding, but urine PEP revealed Bence-Jones proteinuria (M-protein of 5.2 g/24 h). Serum and urine immunofixation electrophoresis showed a zone of restriction in the kappa light chain. In a concurrent bone marrow (BM) study, BM aspirate revealed a diluted feature with no remarkable finding. BM biopsy, however, showed aggregates of atypical spindle-like cells (A). With immunohistochemical staining, the spindle-shaped cells showed positive reaction to kappa light chain (B) and negative reaction to lambda light chain (C). Cytogenetic testing showed normal karyotype. The patient was diagnosed with multiple myeloma (MM) of light chain type. BM examination is a fundamental element in the diagnosis of MM, and the knowledge of unusual presentation of plasma cells such as spindle-like cell morphology would be helpful for a proper hematologic diagnosis.