Epithelial-myoepithelial carcinoma of the bronchus.

An extremely rare case of epithelial-myoepithelial carcinoma (EMC) of a lobar bronchus in a 47-year-old female is reported. Grossly, the tumor formed a polypoid mass obstructing the bronchial lumen. Microscopically, it was composed of two cellular types--epithelial cells with eosinophilic cytoplasm and clear myoepithelial cells. Numerous tubules formed by an inner epithelial and outer myoepithelial layer were found. Focally, the tumor showed solid growth of clear cells. Prominent hyalinization of the stroma was found. The nature of the cells was confirmed by positive expression of cytokeratins and epithelial membrane antigen in epithelial cells and vimentin and smooth muscle actin in myoepithelial cells. Differential diagnosis of EMC includes a broad spectrum of salivary gland-type tumors. Furthermore, metastases of clear cell carcinoma of the kidney or thyroid, clear cell ("sugar") tumor of the lung, glandular form of carcinoid, bronchioalveolar adenocarcinoma with myoepithelial cells and pulmonary adenosquamous carcinoma with amyloid-like stroma must be distinguished from EMC. The tumor has neither recurred nor metastasised, a fact supporting the current opinion, that EMC is a tumor of low grade malignancy.