Pulmonary epithelial-myoepithelial carcinoma: a clinicopathologic and immunohistochemical study of 5 cases.

Pulmonary epithelial-myoepithelial carcinomas are rare low-grade malignant neoplasms with histologic features similar to their salivary gland counterparts. We report a series of 5 cases and describe their clinical, morphological, and immunohistochemical features. The patients included 3 men and 2 women whose ages ranged from 38 to 56 years. All patients had obstructing endobronchial lesions that ranged from 2.5 to 5.0 cm in greatest dimension. The tumors were completely resected by simple lobectomy or pneumonectomy. In one patient, the tumor infiltrated perinodal soft tissue of a peribronchial lymph node with intranodal extension and metastasis within the same lymph node. The follow-up in these patients ranged from 4 to 12 months. The histologic appearance of these tumors varied, but all shared the common feature of a biphasic proliferation of epithelial (strong cytokeratin-positive; actin and S-100-negative) and myoepithelial (strong actin and S-100 and focal weak cytokeratin-positive) cells with formation of bilayered ductlike structures. The focal resemblance to other salivary gland-type tumors may cause diagnostic difficulties, particularly in small endobronchial biopsies. Although little is known about their biologic potential due to limited follow-up data, these tumors when in the lung clearly have the capacity to infiltrate and metastasize and therefore should be designated as epithelial-myoepithelial carcinoma. At present, it appears that treatment by complete surgical resection with negative margins alone is appropriate and adequate.