Ultrastructural and biochemical analysis of "undifferentiated" pulmonary carcinomas.

Seven cases of "undifferentiated" pulmonary carcinoma were studied ultrastructurally; five were of the typical oat cell variety and the remaining two consisted of larger cells. In three of the former and both of the latter cases neurosecretory-like granules were demonstrated. Biochemical analysis of tumor tissue extracts revealed 5-hydroxy-3-indoleacetic acid, vanilylmandelic acid, and catecholamine activity in all instances. No hormonal syndrome or metabolic abnormality was detected in any of the patients. The concomitant morphologic demonstration of neurosecretory-like granules and the presence of 5-hydroxy-3-indoleacetic acid, vanilylmandelic acid, and catecholamines in neoplastic tissue would provide further evidence that these tumors may indeed arise from bronchial endocrine cells and could therefore be classified within the group of neuroendocrine carcinomas. Also it seems apparent that these neuroendocrine bronchial carcinomas may include tumors consisting of cells somewhat larger than the typical oat cell. The observation of 5-hydroxy-3-indoleacetic acid, vanilylmandelic acid, and catecholamine activity in two oat cell carcinomas in which neurosecretory granules could not be demonstrated poses an interesting problem whose solution may only derive from further studies.