Breast cancer in Japan and United States: epidemiology, hormone receptors, pathology, and survival.

Breast cancer is the most common cancer among American women, whereas in Japan it ranks third behind gastric and uterine cancers. In spite of the relatively low incidence of breast cancer in Japan, a sharp increase in the frequency has been noted since 1966, which is decidedly related to change in dietary patterns in Japanese women. An increase of over 250% in dietary intake of fat has been noted during the past 15 years. Cancer is detected at an earlier stage in Japan as compared with the United States, and consequently the end result is significantly better. But the improved results could not be totally explained on the basis of early detection, since stage-for-stage the Japanese series appears to be consistently better than the US series by 10% in their ten-year survival rates.