Mammograms are images difficult to interpret, and a preprocessing phase of the images is necessary to improve the
quality of the images and make the feature extraction phase more reliable. Pre-processing is always a necessity whenever the data to be mined in noisy, inconsistent or incomplete and pre-processing significantly improves the effectiveness of the data mining techniques [12]. This section introduces the pre-processing techniques applied to the images before the feature extraction phase. In the digitization process, noise could be introduced that needs to be reduced by applying some image processing techniques. In addition, at the time that the mammograms were taken, the conditions of illumination are generally different.