Lung endocrine tumours.

The structure of bronchial carcinoids, oat cell carcinomas and pulmonary 'tumourlets' is described and evidence presented that they are related histogenetically, all being derived from certain specialized cells of endocrine or chemoreceptor nature found within the lining epithelium of the airways. Chemoreceptors related to pulmonary blood vessels have also been identified and two different types of pulmonary tumour have both been termed chemodectoma in the belief that they arise from such structures: these are the so-called multiple minute chemodectoma and the larger solitary variety but the exact histogenesis of both these tumours must remain conjectural at present.