Malignant mixed tumor of bronchus: a biphasic neoplasm of epithelial and myoepithelial cells.

This paper describes an unusual malignant mixed tumor of the bronchus arising in a 71-yr-old male and provides evidence of an epithelial-myoepithelial origin based on the findings on light microscopy and immunohistochemistry. The neoplasm contained elements of recognizable benign tumor resembling salivary gland-type pleomorphic adenoma, adenosquamous carcinoma, and a spindle-cell sarcomatous component. Immunohistochemical stains showed the characteristic relationship between epithelial and myoepithelial cells in the benign component of the neoplasm. In addition, the spindle cells stained for myoepithelial markers (S-100 protein and actin) but were also positive for keratin (AE1/AE3). The relationship of this neoplasm to classical carcinosarcoma and the recently described adenosquamous carcinoma with amyloid-like stroma is discussed.