Breast cancer is the most widespread types of cancer among women. An efficient diagnosis in its early stage can give women a better chance of full recovery. Calcification is the important sign for early breast cancer detection. Mammography is the most effective method for breast cancer early detection using low radiation doses. The studies improved the sensitivity of mammogram from 15% to 30% based on Computer Auto-Detection CAD systems, which are used as a “second opinion” to alert the radiologist to structures that, otherwise, might be overlooked. This article summarizes the various methods adopted for micro-calcification cluster detection and compares their performance. Moreover, reasons for the adoption of a common public image database as a test bench for CAD systems, motivations for further CAD tool improvements, and the effectiveness of various CAD systems in a clinical environment are given.