Primary pleomorphic adenoma of the lung with positive staining of TTF-1: a case report and review of literature

Pleomorphic adenoma is a common tumor occurring in the salivary glands of head and neck. But, it is extremely rare in the trachea or lung. Here, we reported a case of primary pleomorphic adenoma of the lung. A 63-year-old man came to our hospital with a tumor in the middle of the trachea nearly obstructing the airway. The histological examination revealed a mixture of epithelial and myxoid-chondroid mesenchymal elements. The tumor tissue was positive for broad-spectrum cytokeratin (CK), CK7, p63, p53, and CK5/6 staining, and focal positive for S-100, EMA, and Vimentin staining. Based on the clinical information, histological features, and the immunohistochemical staining profile, the tumor was diagnosed as a primary pleomorphic adenoma of the lung. Specially, the epithelial cells of this tumor were positive for thyroid transcription factor-1 (TTF-1) staining, which indicated its differentiation toward type II alveolar epithelial cells.