To answer whether a kind of activated fibroblasts in human mammary precancerous tissues, a set of mammary histopathologic frozen tissues, including 21 normal breast tissues (normal), 37 ADH, and 35 DCIS were validated by Hematoxylin and eosin (HE) staining for histopathologic grade and Immunohistochemistry (IHC) staining to identify the activated fibroblasts using their biomarkers of α-smooth muscle actin (α-SMA), fibroblast specific protein-1 (FSP1). Here, S100A4 is linked to ductal breast carcinoma in situ.