Increasing incidence and changing histopathology of primary lung cancer in Japan. A review of 282 autopsied cases.

A total of 282 autopsied cases of primary carcinoma of the lung were reviewed from 1950 to 1983 to determine the incidence of histologic types, sex and age distribution, and to compare the trends between Japan and the United States. There were 75 cases in Group A (1950-1964), 89 in Group B (1965-1974) and 118 in Group C (1975-1983). The overall incidence, 282 cases per 8546 autopsies, was 3.3%; the male-to-female sex ratio was 2.4:1, and the mean age was 62 +/- 11 years. Increases in incidence in men, women, and the total from Group A to C were all statistically significant (P less than 0.05). A predominance of adenocarcinoma over squamous cell carcinoma in all cases was apparent in all the groups, but the data showed a trend toward a reduction in the proportion of adenocarcinoma and increases in the proportion of squamous cell carcinoma and small cell carcinoma. In contrast, an increasing incidence of adenocarcinoma was reported in the USA.