[An autopsy case of sarcomatoid malignant mesothelioma mimicking adenocarcinoma with sarcomatoid elements of lung].

A 62-year-old man with pain in his hip joints and back was admitted to our hospital. His chest radiograph and CT showed a huge mass extending from the left upper pericardium to the left hilum, but no pleural effusion or other lesions. A contrast-enhanced abdominal CT showed multiple metastases to bones and both kidneys. Bronchoscopy revealed obstruction of the left B3 by a visible tumor. The biopsy specimens of the initial immunohistochemical staining were slightly positive for calretinin. However, we diagnosed the condition as sarcomatoid carcinoma of the lung on the basis of the clinical evaluation. Although radiotherapy was administered, his condition rapidly deteriorated and he died due to progression of the disease. Autopsy revealed extensive invasion, suggesting mesothelioma. Therefore, immunohistochemical staining was performed; the findings revealed sarcomatoid malignant mesothelioma. In conclusion, we encountered a rare case of sarcomatoid malignant mesothelioma (stage IV).