Biological features of premalignant disease in the human breast disease

Most human invasive breast cancers (IBCs)(4) arise from preexisting benign lesions. There are many types of benign lesions in the human breast and onl y a few appear to have significant premalignant potential (atypical hyperpl asias and in situ carcinomas). These lesions are relatively common and only a small proportion progress to IBC. They are currently defined by their hi stological features and their prognosis is imprecisely estimated from indir ect evidence based on epidemiological studies. Although lesions within spec ific categories look alike, they must possess morphologically silent biolog ical differences motivating some to remain stable and others to progress. U nderstanding the biological changes responsible for the development and pro gression of premalignant disease is a very active area of medical research. Progress in this area may provide new opportunities for breast cancer prev ention by providing strategies to treat premalignant lesions before they de velop or become cancerous. A large number of biological features have been evaluated in this setting during the past decade. This review discusses a f ew features that appear to be particularly important and have been studied in a relatively comprehensive manner.