Autopsy case of sarcomatoid malignant pleural mesothelioma

A 61-year-old man with a sensation of chest compression was admitted to our hospital. He had hemothorax. After drainage with a chest tube, chest CT scan revealed multiple bilateral pulmonary nodules with slight pleural thickening. Open pleural biopsy was performed and the biopsy specimens showed tumor cells with sarcomatoid proliferation, but no definite epithelial pattern. Initial immunohistochemical staining was negative for keratin and carletinin, but positive for desmin, suggesting rhabdomyosarcoma. After supportive care, he died due to progression of the disease. Autopsy revealed extensive invasion suggesting mesothelioma, so the immunohistochemical staining was repeated. Because it revealed patchy staining for keratin and carletinin, this case was diagnosed as sarcomatoid mesothelioma. Differential diagnosis of sarcomatoid mesothelioma or rhabdomyosarcoma is made by immunohistochemical staining, but it is sometimes difficult. For the selection of the best treatment strategy for mesothelioma especially in the early stage, we should be aware of this difficulty.