FASN and in situ carcinoma: The immunohistochemical staining shown in Fig. 7d depicts how FASN staining was intense in both vehicle- and G28UCM-treated tumors; however, collagen IV staining (a staining against the most abundant collagen molecule present in the basement membrane of breast gland ducts and used in the clinical setting to distinguish invasive from in situ carcinomas) showed that although epithelial cells proliferated and obliterated the ducts in the latter, the basement membrane preserved its integrity in contrast with the architecture-disrupting pattern observed in vehicle-untreated animals.