Mucoepidermoid tumors of the bronchus. Ultrastructural and immunohistochemical study. Histiogenic correlations.

UNLABELLED Bronchial mucoepidermoid tumors are uncommon neoplasms, morphologically similar to their salivary gland counterpart. The histogenesis is controversial. The aim of this study is to identify myoepithelial cells and speculate on their role in the origin of these tumors. METHODS AND RESULTS Sixteen bronchial mucoepidermoid tumor surgical specimens were formalin-fixed, paraffin-embedded and studied using a panel of nine antibodies in order to identify a myoepithelial differentiation. Additional antigens against several cytokeratins were performed in four cases and five of the biopies were studied using the electron microscopy. The different types of cells of the primary bronchial mucoepidermoid tumor (mucous luminal, intermediate and squamous) reacted strongly against AE1, CK7, 34bE12 and weakly with AE3, CK18 and CK8/18/19. S-100, alpha-smooth muscle actin, muscle actin HHF35 and alpha-actinin were consistently negative in all cell types. CD10 was positive in very few cells in just one case. CONCLUSION The immunohistochemical and the ultrastructural study of bronchial mucoepidermiod tumors support a ductal unit origin, without a myoepithelial participation.