Pyothorax-associated lymphoma: Imaging findings

OBJECTIVE. The purpose of this study was to evaluate the radiologic features of pyothorax-associated lymphoma on CT scans and chest radiographs. MATERIALS AND METHODS. Radiographs and CT scans of 21 patients with biopsy-proven pyothorax-associated lymphoma (17 men, four women; median age, 71 years; range 52-77 years) were retrospectively identified. Two readers in consensus analyzed the morphologic imaging features of pyothorax-associated lymphoma and determined their relation to the preexisting chronic empyema cavity. In 13 cases, gallium scans were available and were reviewed. RESULTS. Sixteen patients had a history of artificial pneumothorax therapy for tuberculosis. Pyothorax-associated lymphoma was visualized mainly (71.4% of cases) as extrapulmonary pleural masses on chest radiographs. The CT features included a lenticular (60%) or crescentic (20%) soft-tissue mass located eccentrically at the margin of a coexistent empyema cavity, which was present in all cases. Masses of pyothorax-associated lymphoma were commonly located in the lateral costal pleura (50%) or at the costophrenic angle (30%). The tumor matrix often appeared heterogeneous and contained areas of necrosis (60%). Direct invasion of the chest wall, ribs, lung parenchyma, and abdomen was found in 75%, 50%, 25%, and 25% of patients. Gallium scans, when available, showed marked uptake in 10 of 13 patients (76.9%). CONCLUSION. In patients who have undergone artificial pneumothorax therapy for tuberculosis more than 20 years in the past, a pleural soft-tissue mass adjacent to the margin of a coexistent empyema cavity suggests the presence of pyothorax-associated lymphoma. Knowledge of the typical radiologic findings and locations of pyothorax-associated lymphoma help in the diagnosis of this rare pathologic entity.