Fibrin(ogen) (FN) is an abundant protein, present in human blood at concentrations of 1.5–4 g/L ^[15]. The physiological functions of FN are: besides providing a scaffold for blood clotting, FN is important for the assembly of (extracellular) matrices to enhance host defense ^[16]. FN has been implicated in pathological processes including renal diseases and cancer. Fg-deficient mice (Fg ^−/−) ^[17] were protected from endotoxemia ^[18], renal fibrosis ^[19] and ischemia-reperfusion injury ^[20]. Coagulation factors have been linked with malignancy for over 100 years and high plasma fibrinogen, in particular, has been associated with cancer progression. FN can be produced by cancer cells, such as breast cancer ^[16], and binds to and surrounds cancer cells, forming a protective structure (Figure 1A). Furthermore, by interacting with endothelial cells, FN contributes to the extravasation of cancer cells ^[15]. A hallmark of breast carcinoma is the local synthesis and deposition of fibrinogen (precipitation without conversion to fibrin) ^[21]. FN in the ECM augments the innate immune response to tissue injury or cancer ^[21]. FN deposition is a predominant component in breast tumor stroma ^[21]. All three FN chains were within the top upregulated genes on all three multiplex screens in TNBC and renal models. The multiplex data do not distinguish between fibrinogen and fibrin and do not indicate the involvement of thrombin or other coagulation-related factors. Besides FN upregulation, fibrinolysis inhibitors Serpin A3 (alpha-1-Antichymotrypsin) and alpha-2-macroglobulin were also upregulated on both the tumor and at least one renal screen (Figure 1B).