In addition, cancer progression is not always accompanied by a parallel pain exacerbation: in this regard, increased tumor vascularization and innervation, in addition to infiltration of nerve growth factor (NGF)-producing tumor-associated macrophages observed in a murine model of pancreatic cancer at earlier stage of disease, were not followed by worsening of painful behavior at a more advanced stage [32]. This evidence concerns the gene NGF and pancreatic neoplasm.