FN1 and breast cancer: The main proteins expressed by intratumoral stroma comprise thrombospondin 1 (THBS1), tenascin C (TNC), fibronectin (FN), secreted protein acidic and rich in cysteine (SPARC) and smooth muscle actin-α (α-SMA), which have been reported to be associated with increased invasiveness [6–8], treatment response [9, 10] and poor prognosis [11–13] in breast cancer.