Early detection of breast cancer in the emerging world.

Breast cancer is the number one cancer of women in the world. In middle income countries, and in many low income countries, breast cancer has become the most frequent cancer in women, supplanting cancer of the cervix. In such countries, breast cancer is usually diagnosed at an advanced stage, the majority in stage III and IV, indicating substantial delay in diagnosis. Further, because of the age distribution of the population pyramid, the majority of breast cancers are diagnosed in women under the age of 50. However, that age distribution does not mean that breast cancer is a different disease than in the West. Where population-based cancer registry data are available, it becomes clear that the individual risk for women at every age is no greater than in the West, and in many countries much less.