Epithelial-myoepithelial carcinomas of the bronchus.

Epithelial-myoepithelial carcinomas are very rare in the lung, and little is known about the relationship of their histologic features to prognosis. We describe five primary pulmonary epithelial-myoepithelial carcinomas with details on clinical presentation, histology, and immunohistochemical profiles. We also reviewed the literature to detail further their prognosis. The patients' ages ranged from 33 to 57 years (average 51 years). The tumors were all endobronchial and the patients presented with symptoms or imaging features of airway obstruction. The tumors were completely resected; none showed nodal involvement. All five patients are alive and free of disease 4 months to 8 years (average 4.2 years) after surgery. Four tumors showed a mixed pattern of glands lined by a dual layer of cells and solid sheets of either spindle cells or clear cells, the glandular and solid components being present in variable proportions. The fifth tumor comprised purely spindle cells. The mitotic rate was <1/20 high power fields in both the glandular and spindle/clear cell components. In one case there was focal nuclear pleomorphism. The inner layer of the glands stained for cytokeratins and epithelial membrane antigen, and the outer layer for S-100 and smooth muscle actin. In one case the spindle cells stained for CD34. A review of published cases shows the majority of tumors behave in an indolent fashion, the rare aggressive tumors being predominantly myoepitheliomatous. Nevertheless, the term epithelial-myoepithelial carcinoma is preferred because of their malignant potential. A high mitotic rate, tumoral necrosis, and nuclear pleomorphism appear to be adverse prognostic factors.