Stage Ia malignant pleural mesothelioma: clinical course and appropriate diagnostic process.

Early-stage malignant pleural mesothelioma (MPM) is difficult for physicians to diagnose, and the disease is usually advanced at the time of diagnosis. We report a case of early-stage MPM in a 69-year-old man. The patient presented with fever and left chest pain. A computed tomography scan (CT) of the chest showed a small amount of left pleural effusion and slight left pleural thickening that remained unchanged for 1 year. One month after his inflammatory response spontaneously decreased, follow-up CT of the chest showed reduction in the effusion volume but no change in the pleural thickening. Positron emission tomography with (18)F-fluorodeoxyglucose (FDG) showed increased FDG uptake in the pleural thickening on the left side. Because MPM could not be ruled out, video-assisted thoracoscopic surgery with pleural biopsy was performed for a definitive diagnosis. The postoperative histological diagnosis was early-stage MPM classified as T1a N0M0 disease.