The variation of cell type distribution in lung cancer: a study of 10,910 cases at a medical center in Taiwan between 1970 and 1993.

The rise in the incidence of lung cancer has been associated with shifts in histologic distribution. A study was conducted to investigate changes in the cell type distribution in lung cancer in relation to age, sex, and smoking history, based on a retrospective analysis of 10,910 proven cases of lung cancer at the Veterans General Hospital-Taipei during the period from 1970 to 1993. The diagnosis in each case was substantiated by histologic samples from the original tumor site in the lung. Detailed smoking histories were obtained by personal interview at the time of the first admission. Adenocarcinoma (38.3%) was the most common type of lung cancer, followed by squamous cell carcinoma (37.1%) and small cell carcinoma (12.2%). Over the study period, the incidence of squamous cell carcinoma decreased from 46.4% to 36.2% in men (P < 0.005), adenocarcinoma increased from 30% to 36% in men (P = 0.001) and 50.7% to 64.8% in women (P = 0.008), and small cell carcinoma increased from 7% to 14% in men but showed no significant change in women. Adenocarcinoma exhibited a marked increase in both men and women, and surpassed squamous cell carcinoma as the most frequent type of lung cancer. Lung cancer among younger men, and among non-smoking older men and women, was more often adenocarcinoma. Small cell carcinoma showed a significant increase among males, differing from the trend for squamous cell carcinoma in men, though both are strongly associated with smoking. These findings suggest factors other then cigarette smoking could influence the development and distribution of lung cancer.