DC-LAMP is a molecule expressed in mature dendritic cells, but its mRNA is also found in the lung. This study compares the immunostaining spectrum of PE-10, an antisurfactant protein monoclonal antibody; thyroid transcription factor-1 (TTF-1); and DC-LAMP in normal and neoplastic lung in an attempt to characterize the cell type(s) that express DC-LAMP. Electron microscopy was used to define cell types. DC-LAMP marks pulmonary adenocarcinomas that show Clara cell characteristics by electron microscopy. In contrast, PE-10 labels tumors that have Clara cell and type II pneumocyte differentiation. DC-LAMP staining was lost in solid type adenocarcinomas but persisted in well-differentiated areas. CC-10, an antibody that marks Clara cells, was also positive in tumors that labeled for DC-LAMP. There was no prognostic difference in tumors that reacted with DC-LAMP. DC-LAMP and CC-10 reactivity was also observed in endometrial adenocarcinomas but not in other tumor types.