Chronological changes in latent prostatic carcinoma found in surgical specimens from Japanese during 28 years

Out of 1,193 specimens from open prostatectomies in Japanese at Tokyo Teishin Hospital during the 28 years from 1953 to 1980, 38 focal type latent prostatic carcinomas were found. These were classified histologically by Gleason's criteria and subdivided into two groups, a low grade group (patterns 1 and 2) and a high grade group (patterns 3, 4 and 5). The incidence of the focal type of latent prostatic carcinoma in 1967-1980 was significantly higher than that in 1953-1966 (P less than 0.05). The incidence of the high grade group was significantly higher in the recent 14-year period (P less than 0.05), while the incidence of the low grade group was not. The prevalence of latent prostatic carcinoma in the Japanese male population, especially the prevalence of the high grade group, may have increased during these 28 years, which may be associated with the increasing mortality rate for prostatic cancer in the Japanese.