A 67-year-old male was admitted to the hospital due to fatigue and thrombocytopenia. Peripheral blood cells analysis showed the white blood cells count of 2.99 × 109 /L, red blood cell (RBC) count of 2.08 × 1012/L, platelet count of 15 × 109 /L. β2- microglobulin of serum was 5.50 mg/L. Whole-body positron emission tomography-computed tomography suggested altered reactivity in the lymph nodes of the bilateral neck. Morphological examination of bone marrow (BM) indicated the presence of abnormal smaller lymphocytes, accounting for 12.5% of the total nucleated cells. Strikingly, nuclear fission or brain gyrus nuclei were prominently observed in all abnormal lymphocytes (Figure 1, original magnification 1000×; Wright–Giemsa stain). The proportion of plasma cells was 0.5%, and no morphological abnormalities were observed. Additionally, some RBCs were exhibited a rouleaux arrangement. Flow cytometry analysis of BM identified 16.12% of κ-restricted B lymphocytes expressing CD5- , CD10- , CD19+ , CD20+ . A minimal proportion of 0.03% plasma cells with κ/λ ratio of 1.07. Consistent results were confirmed by immunohistochemistry in the BM biopsy. Immunofixation electrophoresis revealed abnormal monoclonal bands in the IgM and κ lanes. Furthermore, mutations of MYD88 (L265P), CXCR4 (T318fs), and TP53 (R306X) were identified through next-generation sequencing analysis. A diagnosis of lymphoplasmic cell lymphoma/waldenström macroglobulinemia (LPL/WM) was established.