[Large cell carcinoma of the lung: ultrastructural classification, diagnosis, prognosis].

16 lung large cell carcinomas (13 of them were followed for a long time) were studied. It is established that these tumours are a heterogeneous group of neoplasms which may be undifferentiated or with squamous, glandular, oncocytic and endocrine differentiation. Ultrastructural classification is presented reflecting diagnostic and prognostic aspects of these tumours. Tumours with pneumocytes type II, oncocytic differentiation and many lipid inclusions have more favourable prognosis. Unfavourable prognosis is typical for large cell carcinoma formed of undifferentiated cells only or with differentiation in the direction of goblet cells.