Cell proliferation and histologic classification of bronchogenic carcinoma.

The rate of cell proliferation of 99 bronchogenic carcinomas (94 primary tumors and 5 metastases) was evaluated from the labeling index after in vitro incorporation of [3H]thymidine; the rate was then correlated with the histologic tumor type according to the classification of the World Health Organization (WHO). Cell proliferation was significantly slower in adenocarcinoma (WHO type III) than in squamous cell carcinoma (WHO type I), small cell anaplastic carcinoma (WHO type II), and large cell carcinoma (WHO type IV). Cells proliferated at a significantly higher rate in large cell carcinoma than in the squamous cell type, whereas no significant difference was observed between the other cell types. Dedifferentiated forms of squamous cell carcinomas had a higher rate of cell proliferation than did differentiated forms of the same cell type. Metastases of small cell anaplastic carcinoma did not differ in cell proliferation from primary tumors of the same cell type.