SILICA-INDUCED PLEURAL DISEASE - AN UNUSUAL CASE MIMICKING MALIGNANT MESOTHELIOMA

A 57-year-old man with a history of exposure to silica for 32 years pr esented with pleural thickening of the lower lobe of the left lung and a chronic right-sided pleural effusion without any radiographic evide nce of parenchymal nodules in either lung. Light microscopic examinati on of a left visceral pleural biopsy specimen revealed markedly thicke ned pleura with fibrosis and macrophages containing birefringent silic a and silicates. Occasional rounded intrapleural silicotic nodules wer e present. The underlying lung tissue did not show fibrosis or silicot ic nodules. An energy-dispersive x-ray analysis confirmed the presence of silica. In the absence of lung involvement, this case represents a very unusual pathologic reaction caused by silica and silicates and a dds to the clinical differential diagnosis of chronic pleuritis and ma lignant mesothelioma.