A case of malignant pleural mesothelioma with osseous and cartilaginous differentiation.

A 69-year-old man with a history of exposure to asbestos was admitted because of a chest radiographic abnormality. Subsequent findings from computed tomography and a thoracoscopic biopsy suggested malignant mesothelioma. Punctate calcification was observed in the pleural tumor on computed tomography scanning. The patient underwent pleuropneumonectomy, and the tumor was pathologically diagnosed as malignant mesothelioma, sarcomatoid type with osseous and cartilaginous differentiation. Malignant mesothelioma with osseous and cartilaginous differentiation is a rare condition. Punctate calcification in the pleural mass as a lesion distinct from the pleural plaque may indicate osseous or osteosarcomatous differentiation in malignant mesothelioma.