Pulmonary adenocarcinoma of fetal type: alternating differentiation argues in favour of a common endodermal stem cell

Pulmonary adenocarcinoma exhibit different cell types that ultrastructurally, appear to be related to the different epithelial cell types occurring in the terminal lung lobule. The present paper describes the light-microscopical, ultrastructural and immunohistochemical features of a newly defined type of pulmonary adenocarcinoma that resembles an early stage of lung differentiation. The alternating epithelial differentiation within this tumour speaks in favour of a common endodermal stem cell for the different types of epithelial cells within the lung, including endocrine cells. The relationship of this tumour to pulmonary blastoma is discussed.