To explain the association with spleen size and splenomegaly progression, we considered the evidence that increased EDA-FN expression in solid tumors is mostly related with tumor angiogenesis and endothelial activation (15–17), and that neo-angiogenesis and endothelial activation are now documented in the spleen of PMF patients (18–22). This evidence concerns the gene FN1 and Splenomegaly.