Neuroendocrine structures in normal and diseased human lung.

The increasing amount of histological, immunohistochemical and ultrastructural information on some endocrine secretions in human lung cancers suggest the need to revise the classification of neuroendocrine lesions on surgical material. The aim of the present investigation based on lung specimens removed surgically is to give further support to recent proposal for an updated classification of neuroendocrine lung carcinomas. Our study includes 58 squamous cell carcinomas, 58 adenocarcinomas, 6 large cell carcinomas, 27 neuroendocrine carcinomas, and 30 nontumourous cases. Using histological methods (HE, Alcian PAS, Grimelius silver impregnation), we illustrate the presence of neuroendocrine cells and neuroepithelial bodies with their pathological evolutions, ranging from hyperplasia, to dysplasia, and overt neoplasia. On the basis of our experience we propose the following classification of neuroendocrine carcinomas (NEC): typical carcinoids (NECNID), peripheral carcinoid or well-differentiated NEC (NECWED), NEC of intermediate or poorly differentiated type (NECINT) and NEC of small celled or microcytoma type (NECMIC).