A 26-year-old man with no subjective symptoms was referred to our hospital because of a chest radiographic abnormality in the right hemithorax on his chest X-ray (Figure 1A), which was incidentally found during a college health examination. Chest CT revealed diffuse nodular thickening of the right pleura, without distinct pleural effusion and parenchymal lung lesions, mimicking malignant mesothelioma. An initial FDG PET/CT scan demonstrated multiple lesions of intense FDG uptake in the right pleura (maximal standard uptake value (SUVmax) = 10.9) (Figure 2A and Figure 3A). He had no history of pulmonary or autoimmune disease or occupational exposure to asbestos, silica, or other fibrogenic substances. Since the pleural specimens obtained from CT-guided needle biopsy were insufficient to allow for a definitive diagnosis, the patient was admitted for thoracoscopic biopsy.
On admission, right breath sounds were decreased. Remaining physical examinations revealed no abnormal findings. A full blood cell count, the results of liver and renal function tests, and other data were within normal limits. Thoracoscopic biopsy of the pleural tissue revealed caseous necrosis and granulomatous inflammation (Figure 4), although acid-fast bacilli were not found in biopsy specimens. Cultures of sputum and pleural tissue were also negative. However, the QuantiFERON-TB second generation (QFT-2G) test (3.02 IU/ml) and tuberculin skin test (10 mm induration) were both positive based on the Japanese criteria.
Although no positive culture was obtained, other clinical data suggested that a diagnosis of tuberculous pleurisy was highly likely in this case and the patient received antituberculous therapy for 6 months (2HREZ/4HRE) without any side effects. Just after chemotherapy, a repeated FDG PET/CT scan revealed clearly decreased positive signals (SUVmax = 5.7) with marked improvements in pleural thickening (Figure 2B and Figure 3B). Six months after the completion of chemotherapy, a chest radiograph showed further improvements in pleural based opacities relative to that taken just after chemotherapy (Figure 1B and C).