[An ultrastructural classification of carcinomas of the lung]

For the purpose of providing more accurate histological typing of lung carcinoma, it is necessary to classify carcinomas of the lung by electron microscopy. One hundred and fifty cases of resected lung carcinoma were examined under electron microscope. The results of ultrastructural typing of lung carcinoma were as follows: 1. carcinomas showed differentiated features of glandular and squamous epithelium, including squamous cell carcinoma (28 cases), adenocarcinoma (35 cases), and adenosquamous carcinoma (29 cases). Among them, some cases were associated with neuroendocrine differentiation. In addition, solid mucinous cell carcinoma (4 cases) and adenoid cystic carcinoma (2 cases) were seen. 2. Carcinomas showed differentiated features of bronchioloalveolar epithelium, subdividing into clara cell (9 cases), type II pneumocyte (3 cases), mucinous cell (5 cases) and mixed type (4 cases). 3. Carcinomas showed differentiated features of neuroendocrine cell (Kulchitsky cell), including well differentiated (carcinoid, 13 cases), intermediately differentiated (atypical carcinoid, 12 cases), and poorly differentiated (small cell carcinoma, 6 cases). Among them, some cases were associated with squamous differentiation. The ultrastructural classification was compared with histological classification of lung carcinomas and the differences between them are discussed.