Malignant mediastinal tumor with bone formation--mesothelioma or sarcoma?

Mesothelioma can occur in different variants, some of which are difficult or impossible to differentiate from sarcomas. There are scattered reports of sarcomatous mesotheliomas that have osteogenic properties. Here, we report a 57-year old man who presented with a mediastinal tumor containing scattered irregular calcifications with some scattered pleural thickening of the right pleura. Biopsy showed a sarcoma with bone formation. The man was born in the Turkish village of Karain, where the incidence of mesothelioma is extremely high, and a sarcomatous mesothelioma was therefore diagnosed. Since the tumor was pressing against the large vessels and heart, a debulking was performed, followed by Pemetrexed and Carboplatin treatment. However, the tumor grew rapidly and spread to the pleura, involved the heart, and the patient succumbed. This is to our knowledge the first report of a sarcomatous mesothelioma with bone formation from environmental exposure to mineral fibers.