Genesis and source of breast cancer

Premalignancy and cancer risk as indices of cancer origin have become less confusing. Firstly, we are now aware of the time scale of events leading up to clinical presentation, and secondly the nature of probability, inherent to a biological system influenced by genetics, the environment and hormones, is more widely appreciated. Improved understanding of the early phases of cancer, especially origins and sources, stems from correlation of epidemiological, endocrine and histological information. Such data specifically address the modulating influences on structure and activity of breast epithelial units by factors that are linked to cancer risk. Morphology of the normal breast remains a corner stone on which to build concepts of the cellular events involved in the genesis of cancer. Another line of evidence derives from well defined histological characteristics of pathological processes that have been reliably associated with increased cancer risk. These two aspects of analysis encourage belief that heterogeneity is a characteristic of this disease, which has more than one mode of origin and follows variable courses of aggression. In consequence, the aims behind programmes of breast cancer detection and prevention can become more realistic.