Human peripheral lung tumours: light and electron microscopic correlation.

Thirteen human peripheral lung tumours have been studied in both light and electron microscopy. They were classified as epidermoid carcinoma, mucus-secreting cell adenocarcinoma, and alveolar cell adenocarcinoma, the latter made up of granular pneumocytes. Alveolar cell cancer, as defined by ultrastructural features, could assume different gross histological patterns in light microscopy, and therefore electron microscopy is required for its identification.Since neither squamous nor mucous metaplasia was observed in any alveolar cell tumour, it is tentatively suggested that all peripheral lung tumours which lack these features may be derived from granular pneumocytes, irrespective of whether they appear to be adenocarcinomata or large cell carcinomata when examined by light microscopy.