A non-invasive method distinguishes between two types of micro-calcification by x-ray imaging in mammography. Two major types of micro-calcifications are found and confirmed by histopathology and they are correlated to benign and malignant breast lesions. Distinguishing between them non-invasively will significantly improve early breast cancer diagnosis. This is based on the fact that these two types of micro-calcifications show opposite absorption and small-angle scattering signals in x-ray imaging. The imaging system, which can record these two signals of the breast tissue simultaneously for instance, an x-ray grating interferometer, can be used to uniquely determine the micro-calcification type. This is expected to be used in mammography to improve early breast cancer diagnosis, increase diagnosis accuracy and decrease the biopsy rate.