Fine-needle aspiration biopsy of pleural metastases from a carcinosarcoma or true malignant mixed tumor of the parotid gland mimicking a mesothelioma.

Malignant mixed tumor of the parotid is known to have odd sites for metastases. We describe the fine-needle aspiration cytology (FNAC) findings of pleural metastasis from a malignant mixed tumor misdiagnosed as a mesothelioma on cytology at the onset.A 47-year-old man presented to us with breathlessness and a massive pleural effusion with pleural-based nodules. He had been operated 2 years before for a pleomorphic adenoma of the parotid and had a healthy scar at that site. FNAC from the pleural lesions showed myxoid background substance with entrapped cuboidal epithelial cells with atypical nuclei, which were interpreted as mesothelial cells. These cells in contrast to the usual mesothelial cells were not arranged in sheets but rather were huddled in places and formed a pseudoacinar pattern and blended with the myxoid substance.After the diagnosis of a mesothelioma, patient received pemetrexed and cisplatin based chemotherapy with partial response. While on chemotherapy tumor recurred at the primary site in parotid and was confirmed to be a carcinosarcoma on a FNAC and biopsy.To conclude, pleural metastases from a true malignant mixed tumor of the parotid gland can be misdiagnosed as mesothelioma and could occur in the absence of uncontrolled disease at primary site. Both mesotheliomas and pleomorphic adenomas metastatic to the pleura are biphasic tumors, but in a patient with history of pleomorphic adenoma, the latter should be kept as a foremost possibility. Attention to the cytomorphology of tumor cells will also assist in confirming the diagnosis.