A case of malignant lymphoma showing a stratum of lymphoma cells

: A 74-year man suffered an artificial pneumothorax of the right lung because of pulmonary tuberculosis 41 years before. He was admitted, and enlargement of chronic pyothorax was noted in chest radiography in 1998. A 67Ga scintigram revealed uptake at the site of the chronic pyothorax. Cytological findings of the pleural effusion included many atypical lymphocytes. We suspected the presence of a malignant lymphoma and performed a biopsy under thoracoscopy, but could not arrive at a diagnosis. Therefore, resection of the chronic empyema was performed. Histological examination demonstrated the layer of lymphoma cells covering the wall of empyema between the layers of necrotic and connective tissue. Lymphoma cells were stained with L 26, which is known as a B cell marker. We diagnosed diffuse large cell lymphoma (B cell type). No case like this case has ever been published of malignant lymphoma bearing a layer of lymphoma cells. This case is thought to show early-phase malignant lymphoma complicated with chronic pyothorax after artificial pneumothorax. Malignant lymphoma should be suspected when chronic pyothorax undergoes enlargement, even if CT scanning or MRI does not show typical findings.