[Electron Microscopic Classification of Pulmonary Carcinoma]

In a selected group of 175 pulmonary carcinomas the authors demonstrated how electron microscopy renders it possible to respect in their classification more systematically cytological differentiation than when the revised version of the "Histological typisation of pulmonary tumours" published by WHO is used. After electron microscopic examination the group of so-called large cell carcinomas was divided into carcinomas with varying differentiation (small-cell from endocrine cells, pavement cells from keratinocytes, glandular from exocrine cells) and non-differentiated ones (from primitive cells). To the non-differentiated carcinomas those originally small-cell carcinomas were added which lacked ultrastructural differentiation. The uniform subtle structure of glandular carcinomas, however, did not support the importance of differentiation of their subgroups. It became particularly doubtful to have as a separate unit bronchioloalveolar carcinomas when in the group only two bronchiolar carcinomas (from Clara cells) were detected and no carcinoma from alveolar epithelium (from granular pneumonocytes). Double ultrastructural differentiation was found in 10-15% of the carcinomas; their group classification respected the predominating differentiation.