Scanning small-angle x-ray scattering (SAXS) measurements were performed on 36 formalin-fixed breast tissue biopsies obtained from two patients. All samples contained microcalcifications of type II, i.e. formed by hydroxyapatite. We demonstrate the feasibility of classifying breast lesions by scanning SAXS of tissues containing microcalcifications with a resolution of 35 µm x 30 µm. We report a characteristic Bragg peak found around q  =  1.725 nm⁻¹ that occurs primarily for malignant lesions. Such a clear SAXS fingerprint is potentially linked to structural changes of breast tissue and corresponds to dimensions of about 3.7 nm. This material property could be used as an early indicator of malignancy development, as it is readily assessed by SAXS. If this fingerprint is combined with other known SAXS features, which also indicate the level of malignancy, such as lipid spacing and collagen periodicity, it could complement traditional pathology-based analyses. To confirm the SAXS-based classification, a histopathological workup and a gold standard histopathological diagnosis were conducted to determine the malignancy level of the lesions. Our aim is to report this SAXS fingerprint, which is clearly related to malignant breast lesions. However, any further conclusion based on our dataset is limited by the low number of patients and samples. Running a broad study to increase the number of samples and patients is of great importance and relevance for the breast-imaging community.