Molecular pathology of breast cancer

The multistep model of carcinogenesis in the breast suggests a transition from normal epithelium to invasive carcinoma via non-atypical and atypical hyperplasia and in situ carcinoma. The introduction of mammographic screening has led to the increased detection of preinvasive disease, and this has highlighted deficiencies in the biology and classification of such lesions. The excitement surrounding the development of DNA microarray analysis and proteomics has raised expectations about the role of these techniques in understanding the biology and translating these data to clinical practice. Only a few years ago, scientists studied disease initiation and progression in a linear fashion, identifying and examining one cancer-related molecule at a time. The recent development of technologies that allow a large number of genes and gene products to be analysed simultaneously has brought renewed interest to breast cancer research, with the hope of identifying a unique 'fingerprint' for each tumour and hence individualised treatment. To date, histopathological assessment has been at the heart of clinical management – does the new technology herald the end?