Conventional wisdom: observation, experience, anecdote, and science in breast imaging.

Science is and should be the foundation of modern medicine, but observation and experience remain key elements in day-to-day clinical care. As mammography and other breast imaging techniques have evolved, early impressions have been replaced by more rigorous scientific testing, which has led to a more thorough understanding of the breast and the anatomic and morphologic origins of the imaging observations. As is true in many reports that involve the use of a new technique, early information is observational and anecdotal and frequently lacking the all-important "denominator" for a particular observation. For a "sign" to be accepted as a reliable indicator of a process, its associations must be compared with the overall prevalence of the observation in the healthy population. Observed associations must be corroborated by objective analysis.