A 65-year-old man was referred to our hospital due to dyspnea upon exertion. He was an occasional smoker and had been exposed to asbestos from 18 to 20 years old while employed in the construction industry, cutting asbestos-containing building material. Chest X-ray showed left pleural effusion (Fig. 1A), and computed tomographic (CT) images revealed left pleural effusion and calcified pleural plaques without pleural tumor (Fig. 1B). Thoracoscopic exploration revealed red-brown pleural effusion and plaques, but no tumor was detected on the pleura. Culture of the pleural effusion was negative, and cytological examination revealed a cellular distribution of 1.0% macrophages, 1.5% neutrophils, and 97.5% lymphocytes. Other examinations of the fluid showed nonspecific findings. Pleural biopsy showed no evidence of malignancy.
During follow-up, the patient repeatedly exhibited accumulation of left pleural effusion, which was treated each time with thoracentesis. Four years after the first admission, analysis of pleural effusion from the fourth thoracentesis revealed large atypical lymphocytes with distinct nuclear bodies and a high nucleus-to-cytoplasm ratio (Fig. 2). Malignant lymphoma was suspected and thoracoscopic pleural biopsy was performed again, and the biopsy specimen from the fibrin tissues attached to the parietal pleura showed several groups of small round atypical lymphocytes. All of acid-fast bacteria stain, PCR analysis of tuberculosis, and culture for acid fast bacillus were negative. A culture test for standard plate count bacteria was also negative. Immunohistochemical analyses revealed that these cells were CD20+ (Fig. 3), CD3-, CD5-, and CD10-. Based on these findings, the diagnosis was confirmed as diffuse large B-cell lymphoma (DLBCL). Contrast-enhanced CT imaging of whole body (neck to pelvis) revealed no lymphadenopathy or tumor. Serological tests for hepatitis-C virus, human T-cell lymphoma virus-1, and Epstein-Barr virus were negative, as was the immunohistochemical analysis for HHV8. The patient has been followed-up, and has shown no disease progression for 3 years.