Summary

Splenic marginal zone lymphoma (SMZL) is a rare malignant lymphoma involving marginal zone B cells, accounting for only 1% of non-Hodgkin lymphomas. No previous reports have documented SMZL accompanied by massive bloody pleural effusion. Herein, the case of a patient with SMZL that was only diagnosed after splenectomy and thoracoscopic pleural biopsy is presented. SMZL in this patient was accompanied by massive bloody pleural effusion. The characteristics of the patient’s pleural effusion changed from bloody to transudative after splenectomy, and rapid improvement was observed. It was considered that the splenectomy was valid for treatment of unidentified pleural effusion with enlarged spleen.