Abstract: For purpose of providing more accurate histological typing of lung carcinoma, it is necessary to classify carcinoma of lung by electron microscopy.
150 cases of resected lung carcinoma were examined under electron microscopy. The results of ultrastructural typing of lung carcinoma were as follows:
Ⅰ. Carcinomas derived from bronchial surface epithelium and its gland, including squamous cell carcinoma （28 cases）, adenocarcinoma （35 cases）, adenosquamous carcinoma （29 cases）. Among them, some cases associated with neuroendocrine differentiation. In addition, solid mucinous cell Carcinoma （4 cases） and adenoid cystic carcinoma （2 cases） were seen.
Ⅱ. Bronchiolo-alveolar Carcinomas （21 cases） derived froma Clara cell and type Ⅱ Pneumocyte, subdividing into clara cell （9 cases）, type Ⅱ pneumocyte （3 cases）, mucinous cell （5 cases） and mixed type （4 cases）.
Ⅲ. Carcinomas derived from neuroendocrine cell （Kulchitsky cell）, including well differentiated （carcinoid. 13 cases）, intermediate differentiated （atypical carcinoid, 12 cases）, and poorly differentiated （small cell carcinoma, 6 cases）. Among them, some cases associated with squamous differentiation.
The ultrastructural classification was compared with histological clossification of lung carcinomas and the differences between them were discussed.