An 80-year-old man was admitted to the hospital with recurrent chest discomfort and shortness of breath of 2 years' duration, aggravated by back pain over the past 3 days. Physical examination revealed an enlarged spleen III. grade and blood tests showed an increased white blood cell count of 27.03 × 10⁹/l with 62.40% lymphocytes. During hospitalization, the patient's blood pressure suddenly dropped and he went into shock due to a rupture of the upper pole of the spleen, which required emergency surgery. During the surgical procedure, significant bleeding into the abdominal cavity was detected, so a total splenectomy was performed. Postoperative pathology, bone marrow smear, and flow cytometry analysis confirmed the diagnosis of splenic B-cell lymphoma/leukemia with prominent nucleoli (SBLPN). SBLPN is an extremely rare B-lymphocyte tumor of the spleen with a small number of cases reported in the literature. The patient recovered postoperatively without complications, but chemotherapy was not administered due to his poor physical condition.