A true pulmonary carcinosarcoma that required diagnostic differentiation from a pleomorphic adenoma: a case report.

Pulmonary carcinosarcoma is a rarely encountered tumor. We treated a patient who had an intrabronchial polypoid lesion that required a diagnostic differentiation from epithelial-mesenchymal mixed neoplasms inclusive of pleomorphic adenoma, and that was diagnosed by immunohistochemical staining to be a true carcinosarcoma. A 69-year-old man underwent left pneumonectomy in November 2000 with a diagnosis of atelectasis resulting from a tumor obstructing the left lower lobar bronchus, and also a lung abscess. The tumor was initially diagnosed as pleomorphic adenoma, since it contained both benign-looking epithelial and mesenchymal elements, but immunohistochemical staining demonstrated myoglobin-positive rhabdomyosarcomatous elements along with cytokeratin-positive squamous cell carcinoma elements. A definite diagnosis of pulmonary carcinosarcoma was confirmed.