Epithelial-myoepithelial carcinoma of the lung: immunohistochemical and ultrastructural observations and review of the literature.

Epithelial-myoepithelial carcinoma is a rare low-grade malignant salivary gland neoplasm that most commonly occurs in the parotid gland but can also arise in minor salivary glands. We report a case of a primary epithelial-myoepithelial carcinoma of the lung. The patient is a 55-year-old black woman who presented with increasing shortness of breath and productive cough of at least 3 months duration. A left lower lobe endobronchial lesion was identified radiographically. Surgical resection of the lesion was performed, obtaining a circumscribed, nonencapsulated 3.9 cm tan mass which was attached to the inner wall of the lateral basal segment bronchus. A biphasic proliferation of epithelial (cytokeratin positive; S-100 protein and muscle-specific actin negative) and myoepithelial (S-100 protein and muscle-specific actin positive with focal weak cytokeratin positive) cells was identified by immunohistochemical and ultrastructural analysis of formalin-fixed tissue. The patient is disease free 7 months after resection. Pulmonary epithelial-myoepithelial carcinoma likely derives from the submucosal bronchial glands and should be added to the growing list of salivary gland-type neoplasms that may occur as primary pulmonary neoplasms. Because its histology is identical to salivary epithelial-myoepithelial carcinoma, pulmonary epithelial-myoepithelial carcinoma should be considered a low-grade malignant neoplasm and should be designated as epithelial-myoepithelial carcinoma is preference to other terms that may not convey its malignant potential. Although follow-up on reported cases is limited, lobectomy with negative bronchial margin should be curative.