ACTA1 and breast carcinoma: Comparative analyses of Rip1Tag2 pancreatic carcinoma and 4T1 orthotopic breast carcinoma in mice showed distinct overlap of CAF markers, with as many as 43.5% of FSP1/S100A4+ (Box 2) fibroblasts showing co-expression of αSMA in pancreatic carcinoma, whereas only 10.9% of FSP1/S100A4+ fibroblasts showed co-expression of αSMA in breast carcinoma (Sugimoto et al., 2006).