PTN and lung cancer: Pleiotrophin (PTN) is a secretory growth factor with high affinity for heparin.9, 10 In recent years, PTN activity is believed to stimulate the differentiation of neural stem cells, bone progenitor cells and bone marrow stem cells.11, 12, 13 It is also detected in some tumour cells and tumor specimens, and plays an important role in tumor progression, angiogenesis and metastasis.14, 15, 16 However, there is limited clinical research on the over expression of PTN in lung cancer.