A 38-year-old woman was examined at our hospital because of cough, night sweats, and facial edema. Computed tomography of the chest revealed a large mass in the anterior mediastinum measuring 8.2×12.2 cm, with multiple nodules on both lungs. Bronchoscopy revealed multiple nodules parallel to the tracheal rings and obstruction of the anterior segmental bronchus of the right lung. The histopathological features were diagnostic of primary mediastinal large B-cell lymphoma. She underwent chemotherapy followed by radiation therapy to the mediastinal mass. After 8 months, she developed right cerebellar metastasis. Eventually, she received peripheral stem cell transplantation after 17 months.