Centrally located adenocarcinoma with endobronchial polypoid growth: clinicopathological analysis of five cases

Lung adenocarcinomas that exhibit endobronchial polypoid growth and arise from the central portion of the respiratory tree are extremely rare and their clinicopathological features are not well understood. We report the clinicopathological characteristics of five cases of centrally located adenocarcinomas. Histologically, in three cases (cases 1, 2, and 3) the tumor had a papillary, acinar, and solid structure. In the other two cases (cases 4 and 5) histological examination revealed a mucin-filled glandular and cystic structure resembling mucoepidermoid carcinoma, although the lesions lacked a squamoid cell component. Immunohistochemical staining revealed that the tumor cells in all five cases were positive for MUC1 and Cytokeratin 7. The tumor cells in cases 4 and 5 were positive for MUC5AC and MUC6, and the expression pattern in these two cases was similar to that of mucoepidermoid carcinoma of the lung. Our findings allowed us to identify two distinct subtypes of centrally located adenocarcinomas with distinct morphological and immunohistochemical characteristics; these should provide new insight into the pathogenesis of central adenocarcinoma of the lung.