Incidental localized (solitary) mediastinal malignant mesothelioma.

Primary mediastinal mesotheliomas are rare tumours. The mesothelial lining cells of the the pericardium are suggested as the most probable cells of origin. Most of these tumours appear either as a diffuse or nodular thickening of the pericardium that encase and even invade the heart. Localized mediastinal mesotheliomas are distinctly uncommon. We report the imaging findings of a solitary malignant mediastinal mesothelioma that presented mainly as a cystic anterior mediastinal mass. On chest radiography, the tumour appeared as a right paramediastinal soft tissue mass located adjacent to the right middle and lower lobes. On CT, a large, well-circumscribed, right anterior mediastinal mass with a central zone of fluid attenuation was observed. This mass had a thin, smooth wall of uniform thickness as well as a small component that demonstrated soft tissue attenuation. There was no plane of separation between the tumour and aorta/superior vena cava. At surgery the tumour could be dissected easily free from the pericardium and great vessels and it was removed totally. Histopathological examination of the tumour revealed a malignant epitheloid mesothelioma.