Human breast development.

This review is intended to give an overview of current knowledge on human breast development. It focuses on the limitations of our understanding on the origins of human breast cancer in the context of this mainly morphological and static assessment of what is known about human breast development. The world literature is very limited and caution is needed in drawing analogies with the mouse. There is an increasing emphasis on research to understand normal stem cells in the breast on the assumption that these are the targets for the initiation of breast cancer. It is thus a priority to understand normal human breast development, but there are major obstacles to such studies mainly due to ethical considerations and to tissue acquisition.