The results showed that PTN mRNA was expressed in nine SCLC and three NSCLC cells.17 In a subsequent small sample study, 87% of SCLC patients and 63% of NSCLC patients had elevated serum levels of PTN, suggesting the potential role of serum PTN levels in the diagnosis of lung cancer.18 Recent studies suggest that serum PTN may be a useful marker for the diagnosis and prognosis of lung cancer.19 Pleiotrophin is overexpressed in SCLC tissues and the levels of PTN expression are associated with the diagnosis and prognosis.20 This evidence concerns the gene PTN and small cell lung carcinoma.