So-called hamartoma of the lung-a true neoplasm of fibrous connective tissue of the bronchi

A study of 50 so-called hamartomas of the bronchi and lungs, and a review of the literature, revealed clinical and pathologic evidence which was contrary to a developmental origin and supported a neoplastic origin of these lesions. The age of presentation and growth in adults contradicts generally accepted view that they are hamartomas or developmental malformations. The pathologic study shows how the epithelial cell-lined clefts and spaces within the endobronchial type are formed by the inclusion of the overlying bronchial epithelium by the lobular expansion of the connective tissues and cartilage of the lesion. Evidence is then presented which shows that the intrapulmonary type is also endobronchial but is related to small and peripheral rather than large bronchi as in the endobronchial type. Therefore, the epithelial cell-lined clefts and spaces within the intrapulmonary type are also thought to form by the inclusion of bronchial epithelium as in the endobronchial type. Finally, it is shown that the basic component is fibrous connective tissue and the cartilage, bone, fat, and other connective tissues in these lesions arise by differentiation from the basic component.